Yes, there is federal money for sidewalks
There are two pots of federal dollars currently available for Safe Routes to School programs and projects. The first pot is from the old transportation law (SAFETEA-LU), and does not require matching funds. This pot is still available in many states, find out about Pennsylvania here. The second pot of money is from the Transportation Alternatives Program, in the current transportation bill (MAP-21), and it requires local matching funds. Find out how the Pennsylvania Department of Transportation is handling this transition here.
Source: Pennsylvania | Safe Routes to School National Partnership