Aaron Burmeister was the first to leave Nikolai for McGrath, checking out at 12:25 p.m. Tuesday.
Last year's runner up, Aliy Zirkle, followed Burmeister out of Nikolai less than an hour later.
Former Iditarod champions Mitch Seavey and Lance Mackey also departed from Nikolai, at 1:52 p.m. and 2:02 p.m., respectively.
Last year's winner, Dallas Seavey, checked into Nikolai at 11:19 a.m. Tuesday morning and, as of 2:50 p.m. Tuesday, remains at the checkpoint.