By Jennipher Walters,
April 15, 2011

This morning marks one of the biggest days in the marathon running world: the Boston Marathon! With 26,800 people running this year's event and tough qualifying standards, the Boston Marathon draws participants from around the world and is the event for elite and amateur runners. To celebrate today's race, we've compiled a list of five fun facts about the Boston Marathon that you probably don't know. Read on to get your running trivia on!

5 Fun Boston Marathon Facts

1. It's the world's oldest annual marathon. The event began in 1897 and is said to have been started after the first modern-day marathon was held at the 1896 Summer Olympics. Today it is considered one of the world's best known road racing events and is one of five World Marathon Majors.

2. It's patriotic. Each year the Boston Marathon is held on the third Monday of April, which is Patriot's Day. The civic holiday commemorates the anniversary of the first two battles of the American Revolutionary.

3. To say it's "competitive" is an understatement. As the years have passed, the prestige of running Boston has grown-and the qualifying times have become faster and faster. In February, the race released new standards for future races that tightened times by five minutes in each age and gender group. To qualify for the 2013 Boston Marathon, prospective female runners in the age range of 18-34 must run another certified marathon course in three hours and 35 minutes or less. That's an average pace of 8 minutes and 12 seconds per mile!

4. Girl power is in full effect. in 2011 This year, a whopping 43 percent of the entrants are female. The ladies must be making up for lost time as women were not officially allowed to enter the marathon until 1972.

5. It can be a heart-breaker. While it's hard to qualify for Boston, it's not a cakewalk once you're there by any means. The Boston Marathon is known as being one of the toughest courses in the country. Around mile 16, runners encounter a series of well-known hills that culminate in an almost half-mile long hill called "Heartbreak Hill." Although the hill rises only 88 vertical feet, the hill is positioned between mile 20 and 21, which is notorious for when runners feel like they've hit the wall and are running out of energy.

Want to know even more about the marathon? As the Boston Marathon 2011 kicks off today, you can watch coverage of the event live online or track runners progress by name. You can also get fun facts from the race's Twitter account. And be sure to read these running tips from Boston 2011 hopeful Desiree Davila!