Boyd's Directory of the District of Columbia

Boyd's Directory of the District of Columbia was the title of an enormous annual series of directories of people with Washington DC addresses in the early 1900s. I looked at the 1904 edition in particular and found addresses for about 2/3 of the DC patentees. One was clearly identified in the directory as a patent agent, which was not clear from the original patent specifications. Businesses are also in the directory, in principle, but I did not actually find any aero businesses or clubs on first use.

Boyd's Directories for many years are available at the DC History Center, a friendly place at Mt Vernon Square (801 G Street NW) upstairs from the Apple Store. One can make an appointment to look in their research library on Tuesdays or Thursdays from 10am to 3pm. Wikimedia DC has had editathons there. There are also exhibits which I did not have time to look at, both on the 2nd floor and the basement floor.