Part of the Indiana route, according to the RTC, would be the Cardinal Greenway.

INDIANAPOLIS (WTHR) - it's being called the most ambitious project yet for the nation's Rails to Trails Conservancy, a nearly 4,000 trail that would span the United States, connecting parts of 125 exisiting trails.

As the name implies, the route follows now-unused railroad lines and other multi-use paths. The route of the Great American Rail-Trail would be along that of the coast-to-coast railroad charted more than 100 years ago.

“One day, you could go across this entire country on flat, wide, off-road paths. I want rail-trails to be ‘America’s Main Street," said David Burwell, RTC's co-founder.

The project is currently about halfway to completion. The group plans a May 8, 2019 "reveal" of the preferred route of the trail.

Part of the Indiana route, according to the RTC, would be the Cardinal Greenway, "the longest recreational rail-to-trail in Indiana, spanning from Marion to Richmond," according to their Twitter page.