TWIN CHIMNEYS. The Twin Chimneys are two peaks three miles northwest of Post in western Garza County (at 33°13' N, 101°25' W), near the Caprock of the Llano Estacado escarpment as it runs south through the western part of the county. With an elevation of 2,880 feet above mean sea level, the peaks rise 250 feet above Post. The Twin Chimneys are a locally high relief rising from moderately steep slopes surfaced by shallow to moderately deep silt loams that support mesquite and grasses. Along with nearby Duffy's Peak, the Twin Chimneys were used as a landmark in the 1870s by surveyors charting the Llano Ranch (later purchased by Charles William Postqv), as well as other nearby tracts. In 1970 the Texas Historical Commission erected a historical marker at the site.