The Petrolia oilfield, near Petrolia in Clay County, was named for an oil-producing town in Pennsylvania. In 1904 oil was discovered at the site. Though the field never produced large quantities of oil, its shallow depth lessened drilling expenses and made production profitable. On December 17, 1910, a true gusher blew in; Dorthulia Dunn No. One produced 700 barrels a day from a depth of 1,600 feet. The field reached peak oil production in 1914, when 550,585 barrels were taken. Afterward, production declined rapidly, and the discovery of oil at Electra and Burkburnett overshadowed activities at Petrolia. Drilling continued, however, as the field turned out to hold the largest known reserve of natural gas in the state. The first gas well was brought in on May 5, 1907, from a depth of 1,410 feet. Edwy R. Brown began pumping gas to nearby cities and by 1913 was serving Dallas, Fort Worth, and twenty-one other towns. To manage his growing business, Brown formed the Lone Star Gas Company in 1909. The gas Brown pumped to nearby towns contained .1 percent helium. In 1915 the United States Army built the first helium extraction plant in the country at Petrolia, and for several years the field was the sole source of helium for the country. Helium gas production decreased after World War I, and the field ceased operations completely in 1921, when a better source was discovered north of Amarillo.