Auxiliary motor minesweepers were small wood-hulled minesweepers commissioned by the United States Navy for service during World War II. The vessels were numbered, but unnamed. The auxiliary motor minesweepers were originally designated yard minesweepers (YMS) and kept the abbreviation YMS after being re-designated. The type proved successful and eventually became the basis for the AMS type of United States Navy minesweeper. Origin of the YMS The Henry B. Nevins Shipyard, Inc., at City Island, Bronx, designed the YMS and laid the keel of the first one, , on 4 March 1941. Launched on 10 January 1942, YMS-1 was completed two months later on 25 March 1942. From keel-laying to completion, the yard built YMS-1 in one year and three weeks. The "Y" designation The first wooden minesweeper of this class was to gain prominence in all theaters during World War II. A total of 561 were built at various U.S. yards. Originally a class of "motor minesweepers" (MS), "Y" was added to distinguish them from other minesweeper types; sources disagree on whether "Y" stood for "yardcraft" – indicating a type of craft assigned for duty within a navy shipyard or naval base and not expected to go beyond waters adjacent to the base – or to indicate they were built by yacht-builders; YMSs were built at 35 yacht yards, rather than at larger shipyards, 12 on the United States East Coast, 19 on the United States West Coast, and four in yards on the Great Lakes. Use as minesweepers Records show that YMSs were used in the United States Navy to sweep mines laid by enemy submarines as early as 1942 off the ports of Jacksonville, Florida, and Charleston, South Carolina. Many served in the Pacific. One of their greatest losses occurred on 9 October 1945, when seven U.S. Navy YMSs were sunk in a typhoon off Okinawa. The wood-hulled YMS proved to be one of the U.S. Navys more durable and versatile types through a quarter-century of service, filling a variety of roles for a number of navies. Characteristics All 481 ships of this type had the same general characteristics. The only significant variation within the type was one of appearance; YMS-1 through YMS-134 had two stacks, YMS-135 through YMS-445, YMS-480, and YMS-481 had one, while YMS-446 through YMS-479 had none. History Originally rated as service craft, they were used during World War II for inshore sweeping to prepare