The Utah Territorial Legislature approved a plan to locate the capital in the Pahvant Valley.

On October 28, 1851, Utah Governor Brigham Young traveled to the valley and chose the specific site for Fillmore.

The county terrain consists of arid, rough undulating flatlands interrupted by numerous hills and mountain ridges.

[7] The highest point in the county is Mine Camp Peak in the Central Utah Plateaus, at 10,222 feet (3,116 m) ASL.

The Sevier Desert covers much of Millard County, being the seafloor of ancient Lake Bonneville.

About 17 miles (27 km) southwest of Delta, near Black Rock's northwest perimeter is a feature named the "Great Stone Face", which protrudes about four stories above the general elevation.

[10] Locals claim that this rock formation, when viewed at the correct angle, appears similar to a profile of Joseph Smith.

[11][12] At ground level, within view of the "Great Stone Face", is a large, smooth-faced rock covered in Native American petroglyphs.

Millard County is working hard to make it easier to build Earthships, straw bale homes, and other ecological and sustainable housing.

[22] Millard County is the home of the Telescope Array Project ultra-high-energy cosmic ray observatory.

The Lon and Mary Watson Millard County Cosmic Ray Center was dedicated on March 20, 2006.