WASHINGTON COUNTY HISTORICAL SOCIETY (Washington County, Utah)
HIGHWAY 91
ROUTE
US Highway 91 (now called Old Highway 91) came over the mountain from Beaver Dam AZ into Utah. It passed through Santa Clara and followed what is now Sunset Blvd. into St. George at the north end of the Black Hill. Originally, it went down down Diagonal Street to Main Street. Then it followed Main Street down to Tabernacle were it turned east and followed Tabernacle to the east end of town. From there it curved up and went through the Washington Tunnel. Later, its path through St. George was rerouted (as noted below) to follow what is now SR-18 (Bluff Street) south. Then it curved through what is now the Hurst-Ace Hardware property. It then continued east on 100 North (what is now St George Blvd.; see the map). From 900 East, it curved diagonally northeast toward the Washington Tunnel and through the hill. From there it headed diagonally over to what is now Telegraph Road in Washington. It followed what is now Telegraph Road up to and across Highway 9. About 2.5 miles north of Highway 9, Old Highway 91 currently becomes a dirt road for a little less that 2 miles. Continuing on, it passes through Leeds on what is now Main Street (Highway 228). Old Highway 91 continues north along the east side of I-15 to Anderson Junction), where it is now known as Anderson Junction Road. Then ...HISTORY
In 1926, the federal system of numbered highways was initiated, and the Arrowhead Trail became known as US Highway 91. Highway 91 became the principal north-south route through Washington County. In 1931, the final stretch of Highway 91 from Harrisburg through Leeds to Toquerville Junction was paved. US Highway 91 was at its peak from 1947 to 1965. It was superceeded by the I-15 freeway. In 1971, the process was started to drop the US 91 designation. That process was completed by 1974 when all remaining portions of the highway became state highways.Originally, Highway 91 came through St. George by going down Diagonal Street to Main Street. Then it followed Main Street down to Tabernacle were it turned east and followed Tabernacle to the east end of town. From there it curved up and went through the Washington Tunnel. Sometime, maybe in the 1930s, there was a lot of contreoversy ending with Highway 91 being rerouted down Bluff Street and across 100 North to the east side of St. George where it then cut up and through the Washington Tunnel.
REFERENCE
Wikipedia article about Highway 911926 map of the US highway system
A photo tour of Highway 91