that connected to County Road 260. In 1980, vehicle traffic was closed and rerouted to a new road known as County Road 264; although temporary use of the dam as a road continued in 1990. Historical State Markers on the Dam Located on the dam are three state-placed historical markers. These markers are currently inaccessible to the public after foot traffic was disallowed following the September 11 attacks in response to terrorism concerns. 1936 Mountain Valley marker The earliest of the three markers is a 1936 state marker that acknowledges the previous Mormon settlement, Mountain Valley that was built in 1854 and was destroyed in 1913 during construction of the dam. The Mormon settlement Mountain Valley is now located underneath Medina Lake."Established in 1854 by 16 families of Mormons under the leadership of Lyman Wight (1796-1858). They abandoned their homes and mills in 1858 as the result of Indian depredations. Their lands are now beneath the waters of Medina Lake. Erected by the State of Texas - 1936." 1978 Texas Historical Commission Marker The next is a marker placed in 1978 by the Texas Historical Commission that designated the dam as a state historical landmark."Henri Castro, who colonized this area in the 1840s, envisioned irrigated farms along the Medina River. The project was delayed, however, until after the turn of the century, when Dr. Fred Stark Pearson, an internationally known engineer, persuaded British investors to finance construction of a dam at this site. Completed in 1912, Medina Dam was hailed as the largest in Texas and the fourth largest in the United States. Limestone boulders from a nearby quarry added bulk to the massive concrete structure. Four miles downstream, a small diversion dam conducted water into a system of irrigation canals. Gravitational force delivered the water to fields. The outbreak of World War I (1914) disrupted ties with British investors. Seeking new capital, Dr. Pearson and his wife left for England in 1915 on the "Lusitania" and were killed when a German submarine torpedoed the ship. The irrigation network created by Medina Dam brought new prosperity to this region. Vegetables raised in irrigated fields became a valuable crop. Water and electricity were made available to rural residents. In 1925 voters established the Bexar-Medine-Atascosa Counties Water Improvement District No. 1 to manage the project. 1978." 1991 Texas Historic Civil Engineering Marker Placed in 1991, a marker declared the dam a Texas