Paul K. Williams, the House History Map has three cool maps he's created with Google maps.
Two of them plots out the addresses of the different house & building histories he's done for NW DC, and the other for the rest of the city. The third map is of places that have appeared in InTowner's 'Scenes from the past' since April 2001. For the house and building histories you'd just have to contact him through his website WashingtonHistory.com. He also wrote that "I share any and all reports and file copies in the local archives." So I gather it may be with the MLK or the Historical SocietyThe few links from the third map brought up a PDF of the InTowner article.
For more recent history, and probably not so nicely put together, I discovered that the DC Office of Zoning has a database where I can search for things that have come across their plate by case file, street or square. For fun I threw in Square 0521 in the TC. I got BZA case # 13942 with Yong Joon and Young Ja Park . In 1983 their case was approved for the following:
Application No. 13942, of Yong Joon and Young Ja Park, pursuant to Sub-section 8207.2 of the Zoning Regulations for a special exception under Sub-section 7104.2 to change a non-conforming use from grocery store, first floor and basement for storage, to a delicatessen and grocery store, first floor and basement for storage, in an R-4 District at the premises 301 P Street, N.W., (Square 521, Lot 40).
And I was able to look at documents submitted. Oh, DC.gov I just want to hug you. Slowly but surely you are becoming a more open government.