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When Does The Boston Marathon Start? ow.ly

If you yell "Go, Jennifer" to any of the 16,081 women officially running today, you might hit the mark: There are 396 of them, the most common women’s name on the course. They’re joined by 238 Sarahs, 235 Lisas, and 203 Elizabeths.

This year's list of marathon entries reads like a cross between the London and Dublin phone directories. There are 207 Smiths, 146 Johnsons, 110 Browns, 110 Millers, 106 Joneses, and more than 60 Davises, Taylors, Whites, Martins, Campbells, Sullivans, Murphys, and Andersons. The most popular non-English, non-Irish name is Kim, with 51, followed by Gonzalez, with 35. The field includes three runners named Michael Kennedy, and three named Michael J. Sullivan.

The BAA also issued special invitations to the non-runners who were most affected by the tragedy, including victims and their families, and first responders. The Watertown Police Department, for example, is sending a team of 12 officers, including Chief Edward Deveau.

It will take more than two hours for the entire field of 36,000 plus to cross the starting line. The last official runners are expected to begin the 26.2 mile race in Hopkinton only minutes before the women's winner crosses the finish line in Boston.

It would be physically impossible for all the runners to start at the same time, given the narrowness of the streets in Hopkinton, but runners are not penalized for being at the back of the pack. The BAA uses an electronic timing chip that official runners must wear on the back of their bibs to calculate "net" time for each runner -- the difference between when the chip records them crossing the start line, and when it records them crossing the finish line.

Digital clocks displaying elapsed time from the 10 a.m. official start are located at every mile and five-kilometer marker, and times for each runner are recorded at each checkpoint along the way, to make sure no one jumps in the race near the finish line, as Rosie Ruiz famously did in 1980.

Official timing stops six and a half hours after the last runner crosses the starting line, or about 6:10 this evening.

The Boston Marathon starts on Main Street in Hopkinton, two thirds of the way between Boston and Worcester, and follows Route 135 for more than 13 miles through Ashland, Framingham, and Natick to where it joins Route 16 in Wellesley. It continues along Route 16 through Newton Lower Falls, turning right at the red-brick fire station onto Commonwealth Avenue.

From there runners follow Commonwealth Avenue through the Newton hills, bearing right at the Chestnut Hill Reservoir onto Chestnut Hill Avenue to Cleveland Circle. The route then turns left onto Beacon Street in Brookline, and enters Boston with about two miles remaining.

Runners continue through Kenmore Square, near Fenway Park, and under Massachusetts Avenue. They turn right onto Hereford Street, then left onto Boylston Street for the sprint to the finish alongside the Boston Public Library, near Copley Square. The official distance is 26 miles, 385 yards, or 42.195 kilometers.

The first of today's many starts has just taken place in Hopkinton. The group of mobility-impaired runners is off and on their way to Boston after the official starter, Gov. Deval Patrick, waved his hand. There are about 20 mobility impaired entrants, many of whom are running with guides. Their appearance will be the first indication for spectators lining the course that today's events have begun.

This year's field includes runners from all 50 US states and all the Canadian provinces and territories except Nunavut. As expected, Massachusetts leads with 8,088 entries, or 23 percent of the field. California is next, with 2,625 entries, followed by New York (1,775), Texas (1,142), Pennsylvania (1,132), and Illinois (1,027). The mad-for-running Canadian province of Ontario has 1,175 entries.