Is it legal?
Biking on the sidewalk is legal in most of DC, except the Central Business District, show on this map:
It is also legal in Montgomery and Prince George’s Counties, Maryland, and in Virginia except where prohibited by local ordinance.
Is it a good idea?
In a few instances. Read or listen to this WAMU story for a good rundown on the tradeoffs and challenges of sidewalk riding.
If you ride a bike on the sidewalk, you are the biggest and fastest thing in that space. That means it is your responsibility to make sure everyone around you feels safe. Ride slowly, yield to people walking and running, give plenty of space and warning when you’re passing someone.