Seneca is a city located in Illinois. Seneca has a 2020 population of 2,863. Seneca is currently declining at a rate of -0.24% annually and its population has decreased by -2.35% since the most recent census, which recorded a population of 2,932 in 2010. Seneca reached it's highest population of 2,932 in 2010.
The average household income in Seneca is $142,262 with a poverty rate of 1.19%. The median rental costs in recent years comes to $1,085 per month, and the median house value is $287,900. The median age in Seneca is 53.8 years, 54 years for males, and 53.7 years for females.