If that is successful, it would be the first in the Delaware Valley, officials said.
Mayor Michael Nutter participated on behalf of Philadelphia. Commissioners Jim Matthews and Joseph M. Hoeffel were there for Montgomery County, and Commissioner Elizabeth S. Rogan represented Lower Merion Township.
"This is going to be a happy trail," Hoeffel said. "Everybody is going to love it."
The ceremony was held midway across the span, making it a little like prisoner swaps in some old movies.
When the project is finished, a walking and bicycling trail across the bridge will connect Lower Merion Township's recently completed Cynwyd Heritage Trail with the site of a former SEPTA station at Dupont and High Streets in Manayunk.
From there, it's just a short walk to the shops and restaurants of downtown Manayunk.
Preliminary designs for the "park in the sky" show a trail winding among low shrubs and brightly flowering plants on the bridge. There are tall, transparent fence-like barriers to keep hikers from going too near the edge.
The Manayunk Bridge is an S-shaped structure sweeping across the Schuylkill. It dates to 1918. SEPTA acquired the bridge in 1976 to carry its R-6 rail line, but shut it down in 1986 due to disrepair. In 1999, SEPTA began stabilizing the bridge; it's currently sound.
Future phases of the trail project will extend the it to the Ivy Ridge Station and beyond, eventually connecting to the Schuylkill River Trail at Shawmont Avenue.
The project is possible due to collaboration. Contributing in addition to the city and suburbs are SEPTA, the Delaware Valley Regional Planning Commission, Manayunk Development Corporation, the William Penn Foundation, the Bicycle Coalition of Greater Philadelphia, and the Pennsylvania Department of Transportation.
Contact staff writer Bonnie L. Cook at 610-313-8232 or bcook@phillynews.com.