These are currently the 10 largest marathons in the U.S., according to Running USA.
Note: These numbers reflect the 2014 races, which are the most recent numbers available from Running USA.
TCS New York City Marathon50,386 Finishers 1 of 11
The TCS New York City Marathon courses through all five NYC boroughs and draws an estimated 2 million spectators each year. Not only does it top this list, but it's also currently the largest marathon in the world. For many runners, it is a bucket-list race and the epitome of urban running.
Chicago Marathon40,595 Finishers 2 of 11
The Chicago Marathon is known for its fast and flat course, making it a popular race each year for those looking to set a new PR. While registration is limited to 45,000 runners, participants can register by either meeting a time qualifying standard or by being selected through a general lottery. The 2015 race was the 38th anniversary of this historic event.
Photo Credit: Bank of America Chicago Marathon
Boston Marathon31,932 Finishers 3 of 11
Perhaps the most well-known of all U.S. marathons, the Boston Marathon is also the world's oldest, having held its first race in 1897. It is always run on Patriots' Day, the third Monday of every April, and attracts around 500,000 spectators each year, making it New England's most widely viewed sporting event.
Honolulu Marathon21,814 Finishers 4 of 11
The Honolulu Marathon is a popular destination race because of its exotic location, though it can present unique challenges with its tropical weather conditions. Entry to the Honolulu Marathon is open to anyone who can pay the registration fee, typically around $185, with large discounts offered early in the year. Unlike other marathons, there are no qualifying standards to meet, so it's a popular choice for first-timers.
Photo Credit: Honolulu Marathon
Asics Los Angeles Marathon21,508 Finishers 5 of 11
The L.A. Marathon recently celebrated its 30th anniversary and features a popular "Stadium to Sea" course, taking runners by several major L.A. landmarks, from Dodger Stadium to the finish line just a few steps from the Santa Monica Pier. The race is typically held on or near Valentine's Day, so it's a great opportunity to celebrate love with your favorite running partner.
Marine Corps Marathon19,689 Finishers 6 of 11
The Marine Corps Marathon takes place in Arlington, Virginia, the headquarters of the U.S. Marine Corps. Its mission is to promote physical fitness, generate community goodwill and showcase the organizational skills of the United States Marine Corps. The race is known as "The People's Marathon," since it is open to all runners ages 14 and above and is the largest marathon to not offer prize money.
Walt Disney World Marathon19,201 Finishers 7 of 11
Perhaps the most "magical" of all the marathons, this race takes place in Orlando, Florida, and takes runner through all four of the renowned theme parks. Beginning at Epcot, the race continues on to Magic Kingdom, Animal Kingdom and Hollywood Studios before finishing back at Epcot. The course also features Disney characters and entertainment, and finishers receive a Mickey Mouse finisher medal.
Philadelphia Marathon10,359 Finishers 8 of 11
This race is held on the third Sunday of November each year. The course emphasizes the city's history, taking runners past landmarks that include Independence Hall, the Betsy Ross House and the Liberty Bell. Many runners use it as a qualifying race for entry into the Boston Marathon.
Medtronic Twin Cities Marathon8,853 Finishers 9 of 11
The Medtronic Twin Cities Marathon takes place in the Minneapolis-St. Paul area and is also known as, "The Most Beautiful Urban Marathon in America." The course winds around several of the city's lakes and runs along the Mississippi River. Miles 21–25 are a steady uphill climb—considered among the most challenging finishes in American marathons.
Chevron Houston Marathon7,048 Finishers 10 of 11
The Chevron Houston Marathon is the largest single day sporting event in Houston, with around 200,000 supporters and spectators participating. The fast and flat course starts in the downtown area and takes runners through popular areas like Houston Heights, Neartown, Hermann Park and Rice University. The course is a popular choice for runners hoping to qualify for the Boston Marathon.