The closest restroom is at the nearby Lincoln Memorial. Facing the Lincoln Memorial, there is a doorway to the left of the stairs. Go in that doorway to find the restrooms. That is also where you will find the elevator that brings you up to the inner sanctum of the memorial.
There are restrooms neer the monuments also they are small looking buildings
Yes
Bathroom is provided in many museums and government sites. Although not directly to this exact monument.
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