While it may not boast the numbers of the other marathons on the list, Chicago makes the top five as one of the races that make up the "World Marathon Majors." This collective of five races, which all make this top 5, was formed in 2006 and splits a one-million-dollar purse among the top male and female entrants. Chicago is smaller than the other four, but the flat, wide course is known for its speed, and it's a consistent favorite among runners, partially because of the cool conditions during its October slot. Begun in 1977, the Chicago Marathon hosts runners from all 50 states and more than 100 countries.
Though Chicago can host up to 45,000 runners, the maximum number of finishers so far is 33,703 in 2009. The total purse is $485,000, with a cool $100,000 going to both the male and female champion. Sammy Wanjiru set the course record for men in 2009 with a time of 2:05:41. The top female runner, Paula Radcliffe, set the mark in 2002 when she ran the race in 2:17:18. If you want to run the Chicago Marathon, you'll need to pony up the $135 entry fee.