Arnold is a city located in Missouri. With a 2020 population of 21,045, it is the 34th largest city in Missouri and the 1775th largest city in the United States. Arnold is currently declining at a rate of -0.07% annually but its population has increased by 1.14% since the most recent census, which recorded a population of 20,808 in 2010. Arnold reached it's highest population of 21,163 in 2015. Spanning over 12 miles, Arnold has a population density of 1,826 people per square mile.
The average household income in Arnold is $73,408 with a poverty rate of 10.21%. The median rental costs in recent years comes to $955 per month, and the median house value is $153,300. The median age in Arnold is 40.8 years, 37.8 years for males, and 43.2 years for females. For every 100 females there are 99.9 males.