Mt. Pleasant has long been considered the most diverse city in the county, in part because of the liberal Mormons and the Protestant groups which challenged the dominant Mormon population in the late nineteenth century. Liberal Hall, built on Main Street in 1875, and Wasatch Academy, Utah's oldest private boarding school, established by Presbyterians in the same year, remain as visible and functional testaments of the city's historic and ongoing diversity. Mt. Pleasant has been culturally diverse as well, with numerous musical, theatrical, and artistic groups, varied local industries, secret societies and saloons, and one of Utah's largest local historic societies, founded in 1909 and still active.

The twentieth century brought continued changes and improvements to the face of the "Queen City," its most popular nickname. The commercial and residential districts continued to fill with fine buildings bespeaking the prosperity of the community. By 1912 the first high school--North Sanpete--had been completed. The year 1912 also brought the Armory Hall, while the Elite Theater was constructed as a "fireproof" building in 1913. It burned down seven decades later. In 1917 a fine Carnegie Library was built in a modern architectural style. The Marie Hotel was erected in 1920 and a large cheese factory came on the scene in 1930, the same year that bus service came to town. The completion of U. S. Highway 89 in 1936 was a boon needed to soften the impact of Great Depression. A city hall in 1939 and hospital in 1945, together with new schools and churches, gave Mt. Pleasant a full complement of public buildings. Growth has increased in recent decades, as is evidenced by the small new shopping center on the south edge of town.