St. Marys is a city located in Kansas. With a 2020 population of 2,632, it is the 96th largest city in Kansas and the 6656th largest city in the United States. St. Marys is currently declining at a rate of -0.08% annually but its population has increased by 0.19% since the most recent census, which recorded a population of 2,627 in 2010. St. Marys reached it's highest population of 2,658 in 2012. Spanning over 1 miles, St. Marys has a population density of 2,234 people per square mile.
The average household income in St. Marys is $71,980 with a poverty rate of 6.81%. The median rental costs in recent years comes to $709 per month, and the median house value is $144,800. The median age in St. Marys is 26 years, 27.5 years for males, and 24.4 years for females. For every 100 females there are 91.7 males.