New York isn't the only city to be blessed with out-of-use elevated railway-- while back home in Chicago last year, I took a hike on the Bloomingdale Trail, the three-mile-long unused rail embankment that runs through Chicago's residential west side .
The plant-covered trail, which trains stopped using in the 1980's, is just 15 feet tall and runs in close proximity to neighborhood schools, playgrounds, and backyards. Friends of the Bloomingdale Trail  started in 2003 to seize this exciting opportunity to create new community recreation and park space.
Like the High Line, these tracks were initially laid on street level (as part of the Canadian Pacific Railway) in the late 19th Century as part of a comprehensive rail plan for Chicago. They were later elevated to accommodate street traffic.
The City of Chicago is supportive of the plan to use the trail as a park and greenway, and is trying to acquire parcels adjacent to the trail for future access points. The Trust for Public Land  is also on board with helping to acquire these sites.
The project has been recommended for $2.6M in Federal Funding through the Congestion Mitigation and Air Quality Program (an early source of funding for the High Line). Friends of the Bloomingdale Trail is conducting a community visioning survey (with over 700 submitted already), and has planned events to encourage mural painting underneath the trail and other events  to get the word out.
Other similar projects  are on the High Line's Web site.