1. Route description

2. History

3. Major intersections

4. References

5. External links

Idaho State Highway 21 is the Ponderosa Pine Scenic Byway,^[2] primarily a two-lane highway from Boise to Stanley. With two-thirds of its length in Boise County, it passes by historic Idaho City and the village of Lowman to the western edge of the Sawtooth Mountains, then along their northern boundary to Stanley.

The road is designated as one of Idaho's scenic byways and provides access to Sawtooth National Recreation Area from Boise and the Treasure Valley. It primarily follows the Boise River and its tributary Mores Creek to the Boise Basin and beyond, and then the upper South Fork of the Payette River and a tributary from Lowman to Banner Creek Summit.

Route description

State Highway 21 begins at exit 57 of Interstate 84 southeast of Boise, exactly {{convert|3000|ft|m}} above sea level. The highway is an eastern extension of Gowen Road, which runs along the southern and western perimeter of the Boise Airport (and the Air National Guard's Gowen Field) to connect with Orchard Road at exit 52 of I-84.

After {{convert|3|mi|km|spell=in}} eastbound from I-84, Highway 21 descends and crosses the Boise River to connect with Warm Springs Avenue, old SH-21, starting in east Boise. The highway heads upstream, briefly as a four-lane divided highway, along the north bank of the river in a basalt canyon. The route passes the century-old Boise River Diversion Dam and several miles later the Lucky Peak Dam, completed {{Years or months ago|1955}} in 1955.

Above the Lucky Peak Dam, SH-21 climbs over the Highland Valley Summit ({{convert|3782|ft|abbr=on}}), then descends to just above the reservoir. It then crosses the Mores Creek tributary and ascends with it to the Boise Basin gold mining area centered around Idaho City, leaving the sagebrush to enter the Ponderosa pine forest of the Boise National Forest. After Idaho City, the highway continues to climb with Mores Creek for another {{convert|13|mi}} to the Mores Creek Summit at {{convert|6117|ft}}, and with Beaver Creek to the Beaver Creek Summit at {{convert|6041|ft}} {{convert|10|mi|km|spell=in}} further. Following this summit, Highway 21 descends {{convert|2240|ft|0}} in switchbacks to the village of Lowman at {{convert|3801|ft}} above sea level.

At Lowman is the intersection with the Wildlife Canyon Scenic Byway^[3] which descends with the South Fork of the Payette River through a canyon popular for whitewater rafting, westward to Banks at Highway 55. A devastating wildfire ravaged the area around Lowman {{Years or months ago|1989}} in 1989; it destroyed {{convert|45000|acre|km2}} and 26 structures, but without injuries or fatalities.^[4][5]

North of Lowman, SH-21 ascends the South Fork of the Payette River to Grandjean, on the west side of the Sawtooths, and climbs the Canyon Creek tributary to the Banner Creek Summit at {{convert|7056|ft}}, the route's maximum elevation, over {{convert|3200|ft|-1}} above Lowman.

At the Banner Creek Summit, SH-21 enters Custer County and the Challis National Forest, and descends northward with Banner Creek and Cape Horn Creek, tributaries of the Middle Fork of the Salmon River. At "Cape Horn" the highway turns southeast to gradually climb with Marsh Creek to the border of the Sawtooth National Recreation Area, where SH-21 enters the drainage of the main Salmon River, and gently descends to Stanley. About {{convert|4|mi|km|spell=in}} west of Stanley is the turnoff for the {{convert|3|mi|km|adj=on|spell=in}} spur road to the photogenic Stanley Lake at {{convert|6513|ft}}, framed by the jagged McGown Peak at {{convert|9860|ft|0}}.

In Stanley, SH-21 terminates at {{convert|6250|ft|0}} at the junction with SH-75, the Sawtooth Scenic Byway from Galena Summit and Ketchum to the south, originating in Shoshone.^[6] North of the intersection in Stanley, Highway 75 becomes the Salmon River Scenic Byway, and continues due north for a mile, then veers east with the twisty main Salmon River as it descends to Clayton, then north towards Challis, where the route terminates and rejoins US-93 just south of the city limits.^[7]

The upper elevations of Highway 21 are often closed during the winter months,

History

Portions of the highway originated in the 1860s, as a toll road connecting Boise with the gold mining areas near Idaho City.^[8]

Major intersections

References

External links

• Visit Idaho - Ponderosa Pine Scenic Byway
• Motorcycle Roads - Idaho Highway 21
• Mile by Mile - Ponderosa Pine Scenic Byway
• [https://www.youtube.com/watch?v=_Ca3OH1SAMk You Tube video] - Highway 21 Idaho (from motorcycle)
• [https://www.highway21.com Highway21.com] - Apparel named after Idaho State Highway 21

• Gabriella Pregnolato
• Gabriella Quevedo
• Gabriella Rasponi Bonanzi Spalletti Trivelli
• Gabriella Rasponi Spalletti
• Gabriella Remport
• Gabriella Souza
• Gabriellas sang
• Gabriella Szucs (water polo)
• Gabriella Szűcs (water polo)
• Gabriella Szűcs (water polo player)
• Gabriella Tarantello
• Gabriella Taylor
• Gabriella Toth (handballer)
• Gabriella Tóth
• Gabriella Tóth (disambiguation)
• Gabriella Verraszto
• Gabriella Verrasztó
• Gabriella Vu
• Gabriella Wright
• Gabriel Lazaro Mangubat
• Gabriel Lazarte
• Gabrielle Aboudi
• Gabrielle Aboudi Onguene
• Gabrielle Adelman
• Gabrielle Alphen-Salvador