I-90 crosses the Continental Divide over a mountain pass that sits on the border between which two counties ?
Interstate 90:  I-90 crosses the Continental Divide over Homestake Pass just east of Butte, Montana. Homestake Pass:  It sits on the Continental Divide on the border between Jefferson County and Silver Bow County, six miles south-southeast of Butte in Beaverhead-Deerlodge National Forest at an elevation of 6329 ft .
between Jefferson County and Silver Bow County