Jefferson is a city located in Greene County Iowa. It is also the county seat of Greene County. With a 2020 population of 4,020, it is the 99th largest city in Iowa and the 5398th largest city in the United States . Jefferson is currently declining at a rate of -1.01% annually and its population has decreased by -7.48% since the most recent census, which recorded a population of 4,345 in 2010. Jefferson reached it's highest population of in . Spanning over 6 miles, Jefferson has a population density of 674 people per square mile.
The average household income in Jefferson is $61,684 with a poverty rate of 7.24%. The median rental costs in recent years comes to $648 per month, and the median house value is $94,100. The median age in Jefferson is 43.5 years, 38.1 years for males, and 47.3 years for females.