 The first inhabitants were 6,000-10,000 years ago and later came to include Lipan Apache, Mescalero Apache, Coahuiltecan, Jumanos, Tamaulipans, Tonkawa, and Comanches.These tribes settled in rock shelters in the river and creek valleys, leaving behind artifacts and caches of seeds, implements, burial sites, and petroglyphs.Saltillo Alcalde Fernando de Azcué in 1665 passed through the southeast corner of the county on an expedition, becoming the first European to cross the Rio Grande.