• A rare bolide (a comet- or asteroid-like object) hits what is now the lower tip of the Delmarva Peninsula, creating a 55-mile-wide crater. This crater influences the course of the region’s rivers and determines the Chesapeake Bay’s eventual location. As sea levels fluctuate over the next few million years, the area that is now the Bay alternates between dry land and shallow coastal sea.

• (Image courtesy Nicolle Rager-Fuller/NSF)

• A series of ice ages lock ocean water in massive glaciers, causing the mid-Atlantic coastline to extend 180 miles farther east than its current location.
• In warmer periods, a huge glacier melts into the headwaters of the Susquehanna River. In colder periods, thick conifer forests dominate, attracting deer, bears, mammoths and many types of birds.

• (Image courtesy Wing-Chi Poon/Wikimedia Commons)

• Glacial sheets from the most recent Ice Age begin to retreat. The region’s climate begins to warm.

• (Image courtesy Twelvex/Flickr)

• As the climate continues to warm, a landscape dominated by conifers begins transitioning to a mix of hardwood species, such as oak, maple and hickory. 

• (Image courtesy Nicolas T/Flickr)

• Paleo-Indian people using Clovis points first arrive in the region.
• The climate becomes increasingly humid, and the landscape gives way to hardwood forests and coastal wetlands. Paleo-Indians modify their technology accordingly, replacing Clovis points with spear-throwing devices that could be launched over expansive terrain.

• (Image courtesy Ficusdesk/Flickr)

• Ice sheets continue to melt, flooding the Susquehanna, Potomac, James and York rivers and submerging river valleys under hundreds of feet of water. Sea levels continue to rise as water pours into the Atlantic.
• The Chesapeake Bay’s outline begins to form. Ice Age creatures, such as mammoths and giant beavers, are now extinct.

• (Image courtesy Dru!/Flickr)

• Temperatures continue to increase. A mixed deciduous forest habitat much like today’s forests dominates the region. 
• Diverse fish and shellfish populations are abundant in the region’s rivers.
• Acorns and other nuts become a key food source.
• The first oysters colonize the Bay.

• (Image courtesy Chesapeake Bay Program)

• The Chesapeake Bay’s coastline resembles today’s.
• The Bay's waters are dominated by oysters, clams and fish such as bass and shad.
• Native American populations continue to develop more sophisticated hunting methods, such as the bow and arrow. Shellfish becomes an important food source.

• (Image courtesy AerialOutline/Flickr)

• Native American agriculture results in more permanent town villages. Native Americans clear land to grow crops such as corn, squash, beans and tobacco.

• (Image courtesy brandoncripps/Flickr)

• The Chesapeake Bay region is home to only a few thousand humans but many plants and animals, including 200 species of fish, 300 species of birds and 120 species of mammals

• The Native American population reaches 24,000.

Italian Captain Giovanni da Verrazano is the first recorded European to enter the Chesapeake Bay. 

• (Image courtesy F. Allegrini/Flickr)

• While exploring Virginia, Spanish conquistadors capture a young Native American.
• They name him Don Luis and bring back to Spain, where he receives a formal education.

• (Image courtesy barxtux/Flickr)

• Don Luis returns to the Chesapeake region as a guide and interpreter with the St. Mary’s Mission, a group of Spanish Jesuits seeking to establish a religious camp.
• Don Luis quickly abandons the group and returns to his people.
• Months later, he leads a massacre against the St. Mary’s Mission, killing all but one member, a young boy.

• An expedition funded by a private company, The Virginia Company of London, arrives in the Chesapeake Bay.
• They establish the first permanent English settlement in North America at Jamestown, Virginia.

• (Image courtesy Jay I. Kislak Foundation )

• Captain John Smith sets off on his first of two voyages around the Chesapeake Bay. He keeps a journal with detailed descriptions of his surroundings.
• In the years to follow, he draws an elaborate and remarkably accurate map of the Chesapeake Bay and its rivers.

• (Image courtesy National Park Service)

• The tobacco industry is booming in the lower Chesapeake colonies.
• Colonists clear land for agriculture and use hook and line to catch fish in the Bay's shallow waters.
• War and diseases have caused the Native American population to shrink to 2,400, just 10 percent of the size when Europeans first arrived.

• (Image courtesy Trevor Haldenby/Flickr)

• Virginia lawmakers pass a law to prevent wasteful fishing practices on the Rappahannock River.  
• At this time, English settlers begin using hand tongs to harvest oysters.

• (Image courtesy Steve and Sara/Flickr)

• The colonial population grows rapidly as agriculture expands, resulting in the first signs of environmental degradation.
• A patchwork of rural farming and fishing communities develops on the Bay's western and eastern shores.

• (Image courtesy Claude Moore Colonial Farm)

• Colonists strip 20-30 percent of the Chesapeake region's forests for settlements.
• As a result, shipping ports begin to fill with eroded sediment, which makes them too shallow for boats to navigate.
• Commercial fishing for species such as shad and herring begins.

• (Image courtesy SoilScience)

• The colonial population exceeds 700,000. Farmers begin to use plows extensively, starting a cycle of permanent tillage that prevents reforestation and starts a period of massive soil erosion.

• (Image courtesy American Art Museum/Flickr)

• After eight years of fighting, the Revolutionary War ends when British Lord Charles Cornwallis surrenders at Yorktown, Virginia.
• The former British colonies are on the verge of forming a new, unified nation. The Chesapeake Bay region will serve as a key economic and political center.

• (Image courtesy John Trumbull/Wikimedia Commons)

• Virginia and Maryland sign the Compact of 1785.
• Virginia agrees to give vessels bound for Maryland free passage at the Bay’s entrance.
• In return, Maryland gives citizens of both states the right to fish in the Potomac River.

• (Image courtesy NCinDC/Flickr)

• Oyster harvests increase dramatically.
• New England fishermen travel to the Chesapeake with a dredge device that scoops hundreds of thousands of oysters from their beds. Virginia and Maryland eventually ban this equipment.
• Maryland legislation stipulates that only Maryland citizens can transport oysters in the state’s waters.

• Canals, railroads and steamboats provide new transit options.
• Old industries, such as oyster harvesting, as well as new ones, including coal and steel, benefit from these enhanced shipping options.

• (Image courtesy JRiver/Flickr)

• The 25-year Chesapeake & Delaware canal project is completed, linking Chesapeake Bay with Delaware Bay.
• The canal opens undeveloped natural areas to farming and timber harvest.

• (Image courtesy Anthony Bley/Wikimedia Commons)

• Half of the region’s forests have been cleared for agriculture, timber and fuel.
• The first imported fertilizers are used after ships bring bird guano from Caribbean rookery islands and nitrate deposits from the Chilean coast.

• (Image courtesy calwest/Flickr)

• Railroads, canals and steamboats have allowed the oyster market to expand to consumers outside of the Chesapeake region.
• The number of oysters harvested from the Bay has doubled in the last ten years (from 700,000 bushels in 1839 to more than 1.5 million in the 1850s).

• (Image courtesy swamibu/Flickr)

• Water supply systems are constructed to transport drinking water to Baltimore and Washington, D.C.
• Sewer systems are built and send waste and runoff into the rivers that flow into the Chesapeake Bay.
• Brick, stone, iron and steel replace wood as the region’s source of heat, light and building material.

• (Image courtesy Wayan Vota/Flickr)

• Wooden skipjack sailing vessels especially adapted to Chesapeake Bay waters develop as a result of the increased demand for Chesapeake oysters, which were previously harvested on small fishing boats.
• 20 million bushels of oysters are being harvested from the Bay each year.

• (Image courtesy University of Delaware Library/Flickr)

• Nearly 60-80 percent of the forests in the Baltimore-Washington corridor are cleared for agriculture and development.
• Rapidly growing coal-burning industries spew smoke and discharge pollutants into the region’s rivers.
• The Highway Act of 1893 funds the construction of parkways linking cities and suburbs.

• (Image courtesy Nick Humphries/Flickr)

• Railroad tie replacement uses an estimated 15-20 million acres of eastern forests.
• The dramatic drop in oyster populations starts to have an effect on the Bay’s health, and state and federal laws move to control the industry.
• Scientists begin to ask questions about the effects of human activity on the Bay.

• (Image courtesy accent on ecelectic/Flickr)

• A Washington, D.C. law restricts the height of buildings in the city. As a result, the city expands outward.  
• Baltimore installs separate wastewater and stormwater systems to filter water before it flows into the Bay.
• The Migratory Bird Treaty Act outlaws the hunting of whistling swans and sets a limit on international migratory waterfowl. 

• (Image courtesy ghbrett/Flickr)

• Swamps and marshes are drained to create waste dumps and land for new development.  
• The Conowingo Dam, at the mouth of the Susquehanna River, is constructed.
• Upon its completion, it is second largest hydroelectric project by power output in the United States.

• (Image courtesy Cyber Insket/Flickr)

• The Great Depression spurs public works projects that extend the region's roadways, bridges, parks and electrical services to rural areas. This encourages population growth in new areas.
• An interstate conference on the Chesapeake Bay develops the concept of treating the Bay as a single resource unit, rather than separate bodies of water.

• (Image courtesy Beaverton Historical Society/Flickr)

• The “suburb” is born. People begin using synthetic fertilizers on their lawns and fields. Maryland and Virginia create water pollution control agencies.
• The fishing industry increases its range and mobility, causing fish populations to decrease.
• Dermo, a disease that kills oysters, is discovered in the Bay.

• (Image courtesy Virginia Institute of Marine Science)

• The 4.2 mile long Chesapeake Bay Bridge is completed, connecting Anne Arundel County, Maryland, to Kent Island. The bridge opens the Eastern Shore to development.
• Across the region, developers drain and fill wetlands to build new houses, stores and buildings. MSX, a disease that kills oysters, is found in the lower Bay.

• (Image courtesy Radio Rover/Flickr)

• The 17.4 mile long Chesapeake Bay Bridge-Tunnel opens, connecting Virginia Beach to Virginia's Eastern Shore.
• Interstates 66, 70, 83, 95, 270, 495 and 695 are completed.
• The personal car has become the choice transportation mode for Americans.

• (Image courtesy Barabara Rich/Flickr)

• Congress passes the Clean Air Act.

• (Image courtesy Lossanjose/Flickr)

• The Chesapeake Bay Foundation is formed.

• (Image courtesy David Clow/Flickr)

• The increasing forest cover trend reverses due to population growth and development. 
• Increased polluted runoff, as well as damage from Tropical Storm Agnes, destroys the Bay’s underwater grass beds.
• Alliance for the Chesapeake Bay and Susquehanna River Basin Commission form.

• The Clean Water Act is passed. The law establishes water quality standards and limits the amount and type of pollutants allowed to enter waterways.  
• The Endangered Species Act is passed. The law bans DDT and protects endangered species and the ecosystems they depend on.

• (Image courtesy Mr. T in DC/Flickr)

• U.S. Senator Charles Mathias tours the Chesapeake Bay shoreline and sponsors legislation that prompts the Environmental Protection Agency (EPA) to conduct a study on the Bay’s health. This is the first time the Bay’s degrading health is brought to the public’s attention.

• (Image courtesy Pulpolux/Flickr)

• The Chesapeake Bay Commission, a tri-state legislative body, is created.
• The Alliance for the Chesapeake Bay begins a first-of-its-kind program for citizen volunteers to monitor water quality. 

• Maryland, Pennsylvania, Virginia, the District of Columbia, the EPA and the Chesapeake Bay Commission sign the first Chesapeake Bay Agreement. It establishes the Chesapeake Bay Program.

• The Maryland legislature passes the Chesapeake Bay Critical Area Protection Act, a plan to control development near the shoreline of the Bay and its tidal rivers.

• Bay Program partners sign the 1987 Chesapeake Bay Agreement. The agreement sets a goal to reduce nitrogen and phosphorus entering the Bay by 40 percent by 2000. It also directs the Bay Program to study airborne pollution to the Bay.

• Virginia adopts the Chesapeake Bay Preservation Act. This act guides local governments to develop the land in a way that does not pollute the Bay and local waterways.

• The Great Water Bodies Program acknowledges that air pollution contributes to water pollution.
• More than 450,000 acres of land in the region are under nutrient management plans.
• The Maryland Motor Vehicle Administration begins selling “Treasure the Chesapeake” license plates, which support the Chesapeake Bay Trust.

• (Image courtesy Airliners.net)

• Pennsylvania enacts a law requiring large animal farm operations to implement nutrient management plans. One year later, nearly one million acres of land in the Chesapeake Bay region are under nutrient management plans.

• The Local Government Partnership Initiative is signed to provide assistance to the 1,650 local governments in the Bay watershed.

• (Image courtesy adactio/Flickr)

• The Atlantic States Marine Fisheries Commission closes the entire East Coast to Atlantic sturgeon fishing for the next 40 years, the longest fishing moratorium on record.  
• Maryland passes a Water Quality Improvement Act, which forces farming operations to develop a nutrient management plan.

• (Image courtesy Joachim S. Muller/Flickr)

• Chesapeake 2000 sets a goal to reduce enough nutrient and sediment pollution to remove the Bay and its tidal rivers from the EPA's “impaired” water body listing by 2010.
• Maryland records its lowest blue crab harvest, just 20.2 million pounds.  
• The Bay states sign a commitment to provide every student with a "Meaningful Watershed Educational Experience."

• (Image courtesy Brian Talbot/Flickr)

• Approximately 2,869 miles of forest buffers have been restored in the Bay watershed, achieving the Bay Program’s first forest buffer restoration goal eight years ahead of schedule.

• Representatives from headwater states (New York, West Virginia and Delaware) join the Executive Council. 
• The Executive Council recognizes that additional financial resources are needed to continue long-term Bay restoration efforts.
• The Chesapeake Bay Watershed Blue Ribbon Panel is created to seek out new financing opportunities.

• The Executive Council adopts an animal manure management strategy to reduce nutrient pollution from livestock operations.
• Leaders from the watershed states make regional recommendations for the 2007 Farm Bill.

• The Executive Council adopts new directives to increase forest cover, reduce the amount of phosphorous in lawn fertilizer sold in the watershed, and increase funding for farmer assistance programs.
• The nation's first national historic water trail, the Captain John Smith Chesapeake National Historic Trail, is designated.

• (Image courtesy Jane Thomas/IAN Image Library)

• The Executive Council signs the Forest Conservation Initiative.
• NOAA creates the Chesapeake Bay Interpretive Buoy System (CBIBS)
• Maryland launches BayStat, an interactive website that allows government and citizens to track Bay restoration progress.
• The Bay blue crab harvest is among the lowest recorded since 1945.

• Maryland and Virginia issue emergency regulations to reduce the female blue crab harvest to a sustainable level.
• Later in the year, the U.S. Department of Commerce issues a disaster declaration for the Chesapeake Bay’s commercial blue crab fishery.
• The invasive zebra mussel is found in the Maryland portion of the Susquehanna River.

• (Image courtesy Alicia Pimental)

• The Executive Council develops short, two-year goals called “milestones” to measure restoration efforts.  
• President Barack Obama signs an Executive Order calling on the federal government to lead the effort to control pollution and protect wildlife habitats.  
• Annapolis, Md., becomes the first jurisdiction in the Bay watershed to ban phosphorus in lawn fertilizer.

• Maryland, New York and Virginia ban phosphates in dishwasher detergent to help reduce phosphorus pollution to waterways.
• The EPA establishes a landmark Total Maximum Daily Load (TMDL) for the Chesapeake Bay. 
• The Bay Program launches ChesapeakeStat.

• (Image courtesy Lydiat/Flickr)