Its small population live in houses scattered through a number of blocks of rustic streets interspersed with fields and agricultural buildings.

As did most Mormon communities along the Idaho–Utah border, early settlers believed they were in the Territory of Utah.

The 1870 Decennial Census of the United States listed St. Charles and 10 other Idaho Bear Lake Valley settlements under Rich County, Utah.

But when the official survey of the Idaho–Utah line was completed on February 15, 1872, it placed St. Charles and the rest of the northern Bear Lake Valley settlements in Oneida County, Idaho Territory.

In the 20th century it began to attract tourists and persons seeking a recreation area.

Sculptor Gutzon Borglum (1867–1941) was born in St. Charles to Danish immigrant parents.

He is best known for his sculptured portraits of American presidents carved in the stone of Mount Rushmore.

According to the United States Census Bureau, the city has a total area of 0.63 square miles (1.63 km2), all of it land.