In 1855, with the westward expansion, a post office called London was established and served until 1876. Agriculture was the main source of income until 1930 when the discovery of oil a few miles from the community caused a boomtown almost overnight. Another post office was established in 1931, but since there was a post office named London in Southwest Texas, New London was chosen. A tragic school explosion in 1937 killed almost 300 children and teachers. A cenotaph of Texas granite was erected in front of the new school in 1939 in tribute to those who lost their lives in the worst school disaster in U.S. history. Agriculture, cattle and oil-related businesses still form the economy.