Although the Indian, Spanish, and early anglo-American inhabitants knew of this area's large bituminous coal deposits, commercial mining did not begin until 1885, when F. H. Hartz opened a hillside mine near the Rio Grande. For a time, it was the largest producing mine in Texas, but damage from an 1892 fire caused it to close several years later. Hartz then started another mine for the Maverick County Coal Co., which evolved into the Olmos Coal, coke, and Oil Company. Under direction of Pasquale and Rocco DeBona, this company reached a production peak of 1,200 tons a day. Another mining operation was the Eagle Pass Coal and Coke Company, formed in 1893 by Louis Dolch, J. B. Dibrell, and Emil Moshiem. Their mines (.25 miles south) supplied fuel for Southern Pacific Railroad locomotives until 1902. The town of Dolchburg, now called Seco Mines, was built in 1905, with housing for 90 workers. After Dolch's death in 1907, the International Coal Mine Company took over the operation. By 1910, this firm employed 350 men and produced about 1,000 tons of coal a day. Competition from oil, natural gas, and other fuels caused the mines to decline. The main Olmos Co. shafts closed in 1912, but Olmo's Lamar Mine (3.5 miles northeast) and the International Co. Mines were operating as late as 1925. (1975)