PORTLAND – Saturday’s the day to learn more about the Eastern Trail.

That’s when the Eastern Trail Alliance holds its first Trail-A-Thon to call attention to an 85-mile stretch of trail between Kittery and South Portland.

Groups in the 12 communities along the trail will sponsor events including bike rides, walks and educational talks.

“It’s to get people more aware that there is a trail, that it is marked and that you can go from town to town,” said John Andrews, president of the Eastern Trail Alliance.

The trail is part of the old rail bed for the Eastern Railroad. No trains run along the trail now. Instead, the Eastern Trail Alliance envisions a biking and hiking trail extending from Kittery to Casco Bay. The path is part of an even bigger plan to connect Key West, Fla., to Calais with an urban Appalachian Trail known as the East Coast Greenway.

The 37-mile off-road section of the Eastern Trail between South Berwick and Casco Bay is still under development. But the on-road portion between Kittery and South Portland is marked and ready for use.

Bill Heath of the Eastern Trail Alliance, the organizer of the Trail-A-Thon, said the road portion serves a couple of important functions.

“One is to initiate this millennium trail from Florida up to Canada,” he said. “The on-road portion will also serve as an interim route while the off-road trail is being built.”

Eastern Trail enthusiast Peter Chace will host a 50-mile bike ride on the trail to South Berwick.

He’s excited about new signs marking the on-road portion of the trail. The signs are stationed at every major intersection and point the way to the next sign. In many places, the on-road portion of the trail intersects or runs along the off-road portion of the true Eastern Trail.