Treasure Island is a lakeside community located on an island in Lake McQueeney on the Guadalupe River about five miles northwest of Seguin in northwest central Guadalupe County. The upscale development began in the 1950s and offered lakefront lots to many retirees and second homeowners. Though the island suffered extensive damage in the flood of 1972, many residents rebuilt. In 1990 the population was 500. Treasure Island was again heavily flooded in 1998, but by 2000 the population had increased to 600.