Joliet is a town in Carbon County, Montana, United States. It is part of the Billings, Montana Metropolitan Statistical Area. The population was 577 at the 2020 census. The construction of the Rocky Fork & Cooke City Railway in 1892 made Joliet a shipping point. The Joliet Post Office was established on June 10, 1893, with Maud Smith as its first postmaste…Joliet is a town in Carbon County, Montana, United States. It is part of the Billings, Montana Metropolitan Statistical Area. The population was 577 at the 2020 census. The construction of the Rocky Fork & Cooke City Railway in 1892 made Joliet a shipping point. The Joliet Post Office was established on June 10, 1893, with Maud Smith as its first postmaster. The town was named for Joliet, Illinois.