Lake Sammamish Half Marathon

Saturday, March 8, 2025 • Redmond, WA • Course Map

Runners get to enjoy the fast and very flat gravel surface of Washington State’s East Lake Sammamish Trail at the annual Lake Sammamish Half Marathon, which welcomes a few hundred runners every year for a race that unfolds along the trail that stretches between two local parks along the lake here in this suburb of Seattle, Wash.

Organized by 4th Dimension Racing, a locally based running and race management company known for its Evergreen Trail Runs series, the race follows a point-to-point route that starts in Marymoor Park, a 640-acre park just outside Redmond that’s home to several soccer, baseball and cricket fields, and also hosts an annual summer concert series and outdoor movies.

While in the past the race also offered a full, 26.2-mile marathon, since 2011 only the half marathon distance has been offered. Those running the half will start their race at Lake Sammamish State Park at the lake’s southern end, and follow the trail along the lake’s western shoreline all the way northward up to where the finish line lies, in Marymoor Park.

The first two miles of the race unfolds entirely within Lake Sammamish State Park, along the trails that wind through the park, and then runners head out North Sammamish Road.

From there, the course takes runners east toward the trail, which they enter just after passing by the mile 3 marker. Along the route, the half marathon route features gravel surfaces for most of the course (runners will encounter some paved surfaces near both the beginning and the end of the race).

The trail, which stretches 11 miles from Marymoor Park south to the town of Issaquah, lies in the bed of a former railroad and opened in 2006 as a recreational trail for running, walking and biking.

Though there are some gentle rises in elevation over the course of the 13.1-mile half marathon route, runners can expect a mostly flat course for virtually the entire race, organizers note, as this was a large part of the appeal of the route for the marathon and half marathon.

A stretch of the Lake Sammamish Trail as it runs into Issaquah, Washington. (Photo by Robert Ashworth/flickr)

A stretch of the Lake Sammamish Trail as it runs into Issaquah, Washington. (Photo by Robert Ashworth/flickr)

Race Weather & Climate

Located in the northwest corner of the state, just a few miles southeast of Redmond and roughly 20 miles east of Seattle, Sammamish typically experiences March temperatures between 37°F and 54°F. Precipitation is plentiful here in the spring, with an average of just over 6.2 inches of rainfall for the month.

On race day (March 8), the average low is 37ºF and the average high is 52ºF.

Lake Sammamish Half Marathon Past Results

Lake Sammamish Half Marathon Course Map

See the race route map for the Lake Sammamish Half Marathon here.

Starting Time

  • 7:30 AM


  • $72 – $97 for the half marathon

Lake Sammamish Half Marathon Registration

To reserve your spot in the 2025 running of Washington’s Lake Sammamish Half Marathon, register online at here.

Official Race Website


Ever run in the Lake Sammamish Half Marathon? Share your impressions here, or post your review in the Comments below.

See more races in: March, Washington

1 comment… add one
  • Dan Rosslow March 10, 2018, 5:36 pm

    This is one of our favorite runs because of the views, mostly flat course, and the sweat shirt this year was great. I’ve noticed the attendance keeps going down though and my thoughts are it’s because of the after race event. Most races we attend have more variety for taking in calories after the run. I would suggest a few different booths with different items such as muscle milk or bagels like there use to be several years ago. Still love the race and atmosphere but having everybody stand in a long line for the one booth that is serving just a couple of items is my only complaint.


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