Original plans for Fort Mott specified eleven gun emplacements with twenty guns and a mortar battery with six emplacements for Rodman Smoothbore guns. Construction was started in 1872, however, only two of the gun emplacements and two magazines in the mortar battery were completed by 1876 when all work stopped. Fort Mott, along with Fort Delaware and Fort DuPont, became obsolete as the principal defensive installation on the Delaware River with the construction of Fort Saulsbury, near Milford, Delaware, shortly after World War I.