Sabetha is a city in Brown and Nemaha counties in the U.S. state of Kansas. As of the 2020 census, the population of the city was 2,545. …Sabetha is a city in Brown and Nemaha counties in the U.S. state of Kansas. As of the 2020 census, the population of the city was 2,545. The town's settlement began circa 1854, with a name reportedly derived from the word "Sabbath", the day the first settler arrived. Sabetha was incorporated as a city in 1874.