eight Mark 8 torpedoes. Although the General Board had called for two anti-aircraft guns for the O'Brien class, they were not originally outfitted with the weapons; the later was the first American destroyer class so armed. Likewise, there is no record of any of the O'Brien ships being outfitted with mine-laying apparatus. During World War I, most American destroyers were used in anti-submarine warfare roles, and were equipped with depth charges and delivery systems, such as Y-guns and depth charge racks. O'Brien-class ships were equipped with depth charges during the war, but no specific mentions of the types of depth charges used or delivery system are recorded in secondary sources. Comparisons with other "thousand tonners" The "thousand tonners" were the 26 United States Navy destroyers of five classes—Cassin, , O'Brien, , and Sampson—so named because they were the first U.S. Navy destroyers to have displacements greater than 1,000 long tons. The Cassin class, the first of the thousand tonners, displaced about a third more than the preceding . The introduction of the thousand tonners led to the Pauldings and other older, smaller displacement destroyers of previous classes to be dismissively called "flivvers", a nickname also commonly applied to the Ford Model T. The O'Brien class was the third of the five classes of "thousand tonners". The earlier Cassin- (DD-43 to DD-46) and Aylwin-class (DD-47 to DD-50) ships were about the same length as the O'Brien ships and all had median displacements in the range of ; the later Tucker- (DD-57 to DD-62) and Sampson-class (DD-63 to DD-68) ships were about longer and had median displacements of . All five classes were armed with four guns, but the torpedo size and complement varied. All were equipped with four twin torpedo tubes loaded with eight torpedoes except for the Sampsons (which had four triple tubes carrying twelve torpedoes), but the Cassin and Aylwin classes were armed with torpedoes. The O'Brien ships were the first armed with the new Mark 8 torpedoes; the Tucker and Sampson ships also used the 21-inch torpedoes. The Sampsons were the only group originally equipped with anti-aircraft guns, a pair of guns with a caliber of . Construction The construction of the six O'Brien-class ships was allocated to four U.S. shipbuilders. William Cramp constructed a trio of O'Brien destroyers, while the Fore River Shipbuilding Company, Bath Iron Works, and New York Shipbuilding Corporation built one ship each. The