An early route of the Hastings Cutoff ran through the Morgan Valley and down through a narrow gorge in Weber Canyon.

In 1855, Charles Sreeve Peterson and his family became the first white settlers to take up permanent residence in the Morgan Valley after cutting a road through Weber Canyon.

After others began settling in the rather limited planar areas of the mountainous territory, the Utah Territory legislature acted on January 17, 1862, to form a separate county from sections partitioned off Davis, Great Salt Lake, Summit, and Weber counties.

In its southern portion, Main Canyon Creek flows southward from Summit County to join East Canyon Creek, which flows northward from a different portion of Summit County.

At their intersection, a dam has been installed to create East Canyon Reservoir and State Park.

The combined discharge (now called East Canyon Creek) from the dam flows northwestward to Morgan, where it combines with Deep Creek to discharge into the Weber River, which also flows into the county from Summit and follows Lost Canyon to the Morgan Valley.

The terrain generally slopes to the north and west, with its highest point, Thurston Peak, at 9,706 ft (2,958 m) ASL.