Originally Posted by
allset2travel
You can use the Metro and do the Mall at night. Best to alight from Metro at the Capitol South Station. Start from the Capitol building and work your way west. For taking photos, I recommend to bring a tripot. Don't miss the WW II Memorial, its fantastic at night!
When you are done, you probably have to back track to the Smithsonian Station and take the Metro to Crystal City. Be sure to check time for last train.
Just a comment to add here that the above itinerary would involve at least 3 miles of walking if you go all the way to the Lincoln Memorial. That's quite a hike in DC summer heat.
There are also some type of obscure regulations about tripods for cameras in some DC monument/memorial locations, especially at the Capitol building and on the steps of the Lincoln memorial. They are not always permitted, not sure why...