No hassels, reasonable, right out of the 1950's, try the Harrington Hotel. It's on 11th across from the FBI Building, a block from the Ford Theater, walking distance to the National History Museum, a couple of blocks from the Old Post Office, close to a metro station.
It's the place all the schools take the kids for their class trips in the spring. It's safe, Greyline tours picks up there, it has a restaurant.
Definitely no frills and hasn't been updated in half a century, but clean, inexpensive, close to everything. Seriously, it will make you feel like you've stepped back 50 years, which is, I suppose, one of the reasons I like it.