Pleasanton is a city in Linn County, Kansas, United States. As of the 2020 census, the population of the city was 1,208. In 1864, General Alfred …Pleasanton is a city in Linn County, Kansas, United States. As of the 2020 census, the population of the city was 1,208. In 1864, General Alfred Pleasonton defeated the Confederates in the Battle of Mine Creek near present-day Pleasanton. This battle, involving 25,000 men, resulted in a Union victory which ended the threat of Confederate invasion in Kansas.