Dunwich Borers LLC was a pre-war company that owned the Dunwich Building in Washington, D.C.. They made rock-tunneling drills. The company itself was destroyed in the Great War.
The name of the company is a pun on The Dunwich Horror, a short story written by H.P. Lovecraft in 1928.
|The following is based on Fallout 3 cut content and has not been confirmed by canon sources.|
According to cut dialogue from the original version of the Point Lookout quest The Dark Heart of Blackhall, the company was owned by Richard Dunwich, the brother of Constance Blackhall. The dialogue also mentions both Dunwich and Blackhall's shared "obsession with the occult", hinting that the presence of the obelisk underneath the building was not unintentional.
|End of information based on Fallout 3 cut content.|
Dunwich Borers LLC is mentioned in Fallout 3, and is presumed to be the same company which owned the Dunwich Borers location in Fallout 4, before the war.