Colby is a city located in Thomas County Kansas. It is also the county seat of Thomas County. With a 2020 population of 5,464, it is the 59th largest city in Kansas and the 4530th largest city in the United States . Colby is currently growing at a rate of 0.87% annually and its population has increased by 1.43% since the most recent census, which recorded a population of 5,387 in 2010. Colby reached it's highest population of 5,544 in 1980. Spanning over 4 miles, Colby has a population density of 1,474 people per square mile.
The average household income in Colby is $71,123 with a poverty rate of 13.33%. The median rental costs in recent years comes to $634 per month, and the median house value is $125,500. The median age in Colby is 33.3 years, 32.2 years for males, and 34.9 years for females.