David Burwell, the co-founder and first president of the Rails-to-Trails Conservancy, a Washington-based organization that has led nationwide efforts to convert thousands of miles of unused railroad corridors to trails and parklands, died Feb. 1 at his home in Bethesda, Maryland. He was 69.

He had complications from acute myeloid leukemia, said his wife, Irene Burwell.

Inspired in part by his mother, who helped create an 11-mile bike trail on Cape Cod, Massachusetts, Burwell was instrumental in building a national movement to preserve green space and to provide options for alternative modes of transportation.

As thousands of miles of old railroad lines were abandoned each year, some communities across the country remade them as paths for bicycling and nature walks. The Rails-to-Trails Conservancy, which Burwell founded in 1986 with Peter Harnik, became the first group to coordinate national efforts to build such a network.

“It was David who turned ‘rails-to-trails’ from an idea with very good potential into a powerful national force backed by firm legal standing, true political muscle and undeniable financial backing,” Harnik said in a statement released by the conservancy.

The organization was launched with a $75,000 grant from environmental advocate Laurance Rockefeller, who called Burwell “a fireball of energy and determination and talent.”

Burwell and Harnik persuaded officials from the Interstate Commerce Commission to develop regulations that eased the conversion of old rail lines to trails. With his training as a lawyer, Burwell helped untangle thorny right-of-way ownership issues across the country.

In the beginning, the rails-to-trails coalition fought road builders and other entrenched interests before it could claim a place as part of the nation’s surface transportation network.

“The idea of turning unused lines into a vibrant resource unites many people,” Burwell told the San Francisco Chronicle in 1997. “But you get long, skinny parks, cutting across several jurisdictions. Such things fall through the cracks of conventional government. Who has the current title? Who’ll fund the trail, who winds up managing it? That’s where we arrive, to provide expertise.”

In 1991, the conservancy won a major battle with the passage of the Intermodal Surface Transportation Efficiency Act, which mandated that a small portion of federal highway funds be reserved for projects other than paved roads.