While I wouldn't recommend it anywhere, it is only illegal in the central business district ( http://dc.gov/DC/DDOT/About+DDOT/Maps/DC+Central+Business+District+-+No+Bike+Riding+Map+on+Sidewalks+Downtown). Outside of that, I wouldn't go much faster than a normal walker on the sidewalk, so not to interfere with pedestrians and not to surprise cars when crossing driveways.
To follow up with Ryan, timledie, and mrrose….
When you are in street, behave like a car - bike WITH the flow of traffic not against it, stop at stop signs, stop at red lights, and yield to pedestrians when they have the right of way. The ONLY exception is the 2-way bike lanes / cycle tracks (15th St NW & PA Ave NW) and a few other limited spots (NH between 16th and 17th only, and a small lane in Adams Morgan). Bike lanes are marked with the direction you are allowed to bike. Riding the other direction endangers yourself and other cyclists as well as creates unpredictability for cars.
When you ride on sidewalks and in cross walks - yield to pedestrians because they have the right of way. Politely slow down and give a verbal warning when approaching/passing.
Not in DC. That's what the bike lanes are for. BTW, also illegal to run red lights, etc. DC treats bikes as vehicles.
Ryan is correct.
Short answer: YES. Except in downtown.
Thats what bike lanes are for. But we need more bike lanes, especially in the downtown area.
My previous answer was incorrect, as are the rest of the ones here except for AL's:
Page 2 from the official DC Department of Transportation regulations summary:
"Must yield to pedestrians. Allowed in the city with the exception of the central
business district (bounded by
Massachusetts Ave. NW, 2nd St NE
SE, D St SE/SW, 14th
St NW, Constitution Ave and 23rd St NW)"
Please ignore the bad info here from "JK" and "SloopJohnB" and "Greg" because the answers they made are incorrect. You can verify yourself here:
As a side note, this q&a thing is pretty useless if you can't downvote bad information.
Bad information from JK and SloopJohnB. It may be annoying to pedestrians at times, but it's one hundred percent legal to bike on the sidewalk (outside of the central business district) even in the presence of a parallel bike lane. Cyclists must yield to pedestrians on the sidewalk, though. Also, cyclists in the street are not compelled to use bike lanes, even when they're present. This is in recognition of the fact that in some situations it's safer to take the car lane than the bike lane.
It's extremely dangerous, but it is legal. I never ride on the sidewalk unless the road is completely impassible, such as on 11th St SE just south of M St SE where the bike lane is blocked by a 6" high pile of asphalt. One big problem is that when bicyclists use the sidewalk they think like pedestrians and don't look for other bikes, just for cars. This is why so many of pedestrians and "sidewalk bikes" jump out in front of me even with a "don't walk" sign.
You may only ride in a bicycle or traffic lane.
If you are on the sidewalk, you must dismount and walk your bicycle.
(mrrose was correct as well)