From a total population of 9,321, Monmouth has a median age of 33.3. The average age of males, in Monmouth, is 28.3 while the average age of females is 35.8. When you compare this to median age of Illinois, Monmouth is 3.7 years younger.
The median income of individuals, in Monmouth, is $19,431 while the average household income is $36,291. When comparing the median income of people living in Monmouth to the rest of Illinois, the average income in Monmouth is $10,588 less.