The city was named for Samuel Hardin, a friend of developer Charles Henry Morrill.

[7] According to the United States Census Bureau, the city has a total area of 2.57 square miles (6.66 km2), all land.

Hardin hosts a bitcoin mining facility by Marathon Patent Group, according to a press release by the company in 2021.

[15] In 2004–05, a consortium including architectural, bond sellers and contractors located in Texas, promoting the construction of speculative prison and jail ventures [16] convinced Hardin's industrial development authority to float a $27 million bond issuance to build the Two Rivers Detention Facility.

[18][19] The consortium's contract terminated in January 2009 without any prisoners ever being housed in the jail.

[22] It remained complete and vacant for over seven years, though it was partially filled for 18 months.

By February 2016, empty once again, it had cost the city $582,595 paid to Two Rivers to maintain it since 2004.

[23] Due to unpaid interest on the defaulted bonds, its estimated indebtedness had increased to over $40 million by December 2015.

[24] In April 2019, the Bureau of Indian Affairs took possession and began operations.

[25] The Big Horn County Historical Museum is located in Hardin.

[26] The Hardin Area Chamber of Commerce and Agriculture conducts the annual Little Big Horn Days festival the 3rd weekend in June.

It includes the Custer's Last Stand Reenactment written by Joe Medicine Crow.

[27] The Hardin School Districts educate students from kindergarten to 12th grade.