In 1991, a group of cyclists and long-distance trail enthusiasts met in New York City and formed a national non-profit organization, the East Coast Greenway Alliance (ECGA), to plan and promote a greenway linking existing and planned trails into a contiguous "spine route" between Atlantic coast cities.
A planned alternative to the Richmond-Wilmington leg of the journey hews closer to the coast, passing through Virginia Beach in the Tidewater region and continuing on through the Elizabeth City, Greenville, New Bern and Jacksonville in North Carolina before rejoining the main line near the mouth of the Cape Fear River at Wilmington. Other alternate routes are planned for Maine, Massachusetts, and Florida.
Maryland's 164-mile (264 km) spine route of the East Coast Greenway takes a jagged S-shaped course across urbanized Central Maryland. It travels from Delaware due west to the Northern Central Rail Trail, turns south to pass through Baltimore and then southeast to Annapolis, and then turns west and winds toward Washington, D.C. There is also a branch of the East Coast Greenway across the Chesapeake Bay on the Eastern Shore: it starts just past the Delaware state line and travels south across the Delmarva Peninsula to reach the Cross Island Trail, then crosses the Chesapeake Bay Bridge to rejoin the spine route in Annapolis.
Maryland is the only state on the East Coast Greenway where motorist assistance is required on the spine route: the Thomas J. Hatem Bridge over the Susquehanna River has no bicycle or pedestrian accommodations. A crossing service was once provided by Biller's Bikes in Havre de Grace. In 2012, Harford Transit began regular bus service across the bridge with buses equipped with two-bike racks. On the Eastern Shore Route, bicycles are prohibited on the Chesapeake Bay Bridge, and there is no crossing service there at all.
Two future trails are expected to become parts of the East Coast Greenway: the South Shore Trail between Odenton and Annapolis and the connection of the two pieces of the Washington, Baltimore and Annapolis Trail (WB&A). The WB&A's segments are separated by the Patuxent River and a property dispute.