McHenry Dam, officially known today as the William G. Stratton/Thomas A. Bolger Lock and Dam, has a long history tied to construction, navigation, flooding, and recreation on the Fox River. Before 1816, historic accounts describe large stone slabs placed across the river, probably by the Potatatomi, to aid crossings, and early pioneers later used those slabs as hearthstones. In 1887, steamboat operators built a dam to raise water levels for boating, while farmers opposed it for fear of losing land to rising water. In 1901, Senator William Lorimer supported the newly formed Fox River Navigable Waterway Association by lobbying for a new dam, and in 1907 the association secured a federal permit and built a wooden dam that raised Fox Lake by six feet and helped create recreational waters along the Chain of Lakes, spurring hotel and saloon growth in Fox Lake by 1910. From 1912 to 1915, the rotted wooden dam was replaced with steel pilings and removable flashboards, and a concrete lock was added on the east side to allow navigation around the structure. From 1919 to 1923, the Fox River and Lakes Improvement Association assumed control of the dam, but financial problems led it to transfer responsibility to the Illinois Department of Public Works. After the flood of 1938, the Illinois Division of Waterways and the Civilian Conservation Corps built the present concrete dam in 1938 and 1939, using boulders donated by the Bolger family. In 1953, James Hughes sold a strip of land to the State of Illinois for one dollar to support improvement and maintenance of the waterway. Public hearings in 1958 to 1960 led residents to choose construction of a new lock and bypass channel, completed at a cost of $285,000, and the lock opened to the public in 1960. Repair funding and basin study money were allocated in 1982 and 1983. In 1991, the McHenry Lock and Dam was renamed the William G. Stratton Lock and Dam in honor of Governor Stratton, a longtime supporter of the dam. Floodgates were installed in 2002 to improve flood control, the state invested in park improvements east of the dam in 2003, and in 2014 the William G. Stratton/Thomas A. Bolger Life Extension Project began, including removal of five sluice gates, installation of new water control gates, and extension of the lock.