There are many Blue Mountain's, and this one is located in Snohomish County, WA and just east of Sultan. From parking gate to summit, it involves a 3 mile road hike (6.1 miles round-trip), and ~1,300 feet of gain. There are some views along the way, and limited views from the summit. With the summit being heavily wooded, I activated near the tower (west / northwest of the summit and ~40 feet below summit per CalTopo map). Was able to spot from the summit, but AT&T service was not consistent.
Directions: