Lake Lyndon B. Johnson (more commonly referred to as Lake LBJ and originally named Lake Granite Shoals) is a reservoir on the Colorado River in the Texas Hill Country in the United States. The reservoir was formed in 1950 by the construction of Granite Shoals Dam by the Lower Colorado River Authority.he lake was originally called Lake Granite Shoals. The dam would be renamed Wirtz Dam in 1952 for Alvin J. Wirtz, the first general counsel of the LCRA, and the lake was renamed to Lake Lyndon B. Johnson in 1965 in honor of US President Lyndon Baines Johnson.