Head to Cougar Mountain Regional Wildland Park in Bellevue for this trail running series organized by Seattle Running Club and Northwest Trail Runs, where you'll tackle well-marked single-track trails through beautiful forest with rolling terrain just 15 minutes from Seattle. Choose between Short or Long Series formats and compete across multiple race distances from May through August (plus an October finale), with your best 3 out of 4 races counting toward awards. Every entry contributes $15 to King County Parks, and you'll enjoy post-race food and drinks—just remember to bring your own refillable water bottle and leave your dog at home.