 US-89 meets the current alignment of US-91 in the southern outskirts of Brigham City, turning east for an overlap on the city's southeast bypass. (SR-13 and SR-90 are the former alignment through Brigham City.) The two routes head east up Box Elder Canyon in the southern Wellsville Mountains, finally leaving the valley of the Great Salt Lake into a small valley that contains Mantua Reservoir (elevation 5200 feet / 1585 m). US-89 / US-91 turns north there, bypassing the town of Mantua to the west, and continues to ascend through Dry Canyon to Sardine Summit (elevation 5900 feet / 1798 m). Another small valley leads to Wellsville Canyon, where the four-lane roadway again turns east and descends into the Cache Valley. In that valley, US-89 / US-91 heads northeast, bypassing Wellsville to the east, into downtown Logan. US-91 continues northerly from Logan into Idaho, but US-89 splits to the east, beginning a long climb of the Bear River Range through Logan Canyon. The Logan Canyon Scenic Byway, a Utah and National Scenic Byway, begins at Logan and follows US-89 up the canyon, past the access road to the Beaver Mountain ski area, to Garden City and on to the state line. Bear Lake Summit (elevation 7800 ft / 2377 m), at the top of the range, is the highest point on US-89 in Utah, from which it descends the east slope via horseshoe curves to Garden City on the shore of Bear Lake (elevation 5900 ft / 1798 m). The final segment of US-89 to the Idaho state line follows the lake's west shore, its location constrained by the Bear River Range just to the west.
