Langdon is a city in Cavalier County, North Dakota. It is the county seat of Cavalier County. The population was 1,909 at the 2020 census. Langdon was designated as the county seat in 1884, was founded in 1885, and was incorporated on February 25, 1888.

A post office has been in operation in Langdon since 1886. The city was named for Robert Bruce Langdon, a politician and railroad official.

On October 29, 1887, The Courier, an early Langdon newspaper, reported that Rosa Lake, Lemon, Olga, and Langdon were all vying for the position of county seat. Anecdotal stories tell of several settlers who succeeded in voting several times by simply changing their hats and coats. When all votes were tallied, it was found that Langdon had polled 301 votes, Olga 246, Rosa Lake 55, and Lemon 11. It was alleged that the Langdon precinct had cast 150 votes with a total of only 50 qualified voters. However, the county seat remained in Langdon.

​To Learn more about the city of Langdon click here.