Waldron is a city in Harper County, Kansas, United States. As of the 2020 census, the population of the city was 9. The south edge of the city i…Waldron is a city in Harper County, Kansas, United States. As of the 2020 census, the population of the city was 9. The south edge of the city is the Kansas / Oklahoma state border. Waldron was founded about 1900. The first post office in Waldron was established in 1902. In the 1901-1902 timeframe, Waldron became the point where the rail lines of the Choctaw Northern Railroad and the Kansas City, Mexico and Orient Railway crossed. Both lines through the town were subsequently abandoned.