|The following is based on Van Buren and has not been confirmed by canon sources.|
The MacArthur Army Base is a military facility in 2253.
In a random encounter around New Canaan, the player character will find a squad of Enclave troopers that will approach them, asking for directions to the MacArthur Army Base.
If the player character is hostile or "weird" the troopers will open fire on them.
MacArthur Army Base was mentioned only in Van Buren, the canceled Fallout 3 by Black Isle Studios.