Arizona State Route 51

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State Route 51

Piestewa Freeway
SR 51 highlighted in red
Route information
Maintained by ADOT
Length16.70 mi[1] (26.88 km)
Major junctions
South end I-10 in Phoenix
Major intersections Loop 202 in Phoenix
North end Loop 101 in Phoenix
CountryUnited States
Highway system
  • Arizona State Highway System
SR 50 US 60
The Piestewa Freeway at its southern terminus, the "mini-stack" with Interstate 10 and Loop 202. Photo looks north as SR 51 winds through residential areas and the Phoenix Mountain Preserve.

Arizona State Route 51 (SR 51), also known as the Piestewa Freeway, is a numbered state highway in Phoenix, Arizona. It connects Interstate 10 just outside Downtown Phoenix with Loop 101 on the north side of Phoenix, making it one of the area's major freeways. It is a largely north–south route and is known for traversing the Piestewa Peak Recreation Area. The peak was named after Lori Piestewa, the first Native American woman to die in combat in the U.S. military. Prior to this time, the freeway was known as the Squaw Peak Parkway, a name considered offensive by Native Americans.[2] Rapid growth and increased traffic demand on the east side of Metro Phoenix made the Piestewa Freeway necessary.

The freeway was proposed at least as far back as 1955. It was intended to become part of a never-constructed Interstate 510.[3]

Route description

SR 51 begins at an interchange with I-10 and Loop 202 immediately east of downtown Phoenix. The route heads north from the interchange through the northern sections of Phoenix. The freeway travels through some major areas of Phoenix and past some major services such as the Phoenix Children's Hospital, Arizona Heart Hospital and Heart Institute, and the Camelback Colonnade at 20th Street and Camelback Road. The highway then begins to climb to the top of Dreamy Draw, a mountain passage between Piestewa Peak and North Mountain, before descending into the Paradise Valley area of North Phoenix. It reaches its northern terminus at a three-way interchange with Loop 101 by Desert Ridge. The entire length of SR 51 features HOV lanes.[4]


Interstate 510

The Phoenix inset from an early plan for the Interstate Highway System showing what would become the Piestewa Freeway as a spur from what would become Interstate 10.

General Location of National System of Interstate Highways, a 1955 proposal for what would become the Interstate Highway System, included a spur freeway from what would become Interstate 10, proceeding north along a route similar to the modern Piestewa Freeway. The road was later designated I-510.[3] The routing of the freeway later appeared in route logs in 1968 under the designation of State Route 510 and the name Squaw Peak Freeway.[5]

The freeway was originally named the Squaw Peak Parkway. The modern usage of the word squaw, which can be perceived as a derogatory term for Native American women, had led to guidelines from the U.S. Board on Geographic Names that the word should be phased out of the names of natural features.[2] In 2003, Governor Janet Napolitano announced her intent to rename the peak for which the freeway was named.[6] That same year, U.S. Army specialist and Arizona native Lori Piestewa was killed in the 2003 invasion of Iraq. According to U.S. Army records, Piestewa was the first known Native American woman to be killed on foreign soil while serving in combat for the military.[7] As such, Governor Napolitano thought this was an appropriate new name for the peak, which by extension affected the name of the freeway.

The original five miles (8 km) of the freeway between McDowell Road and Glendale Avenue were constructed by the city of Phoenix (as the Squaw Peak Parkway) between 1986 and 1991. The first overpass to be completed was in 1986 at Osborn Road.[8] In 1987, the bridge over the Grand Canal had been completed, as well as the overpass at McDowell Road and the southbound connector to eastbound I-10.[8][9] On December 18, 1987, SR 510 was renumbered SR 51. Also completed in 1987 were the overpasses at Colter Street and Missouri Avenue that passed over the freeway. Several more overpasses were completed in 1988 including those located at Indian School Road, Highland Avenue, Camelback Road and Bethany Home Road.[8] Also in 1988, the state established a corridor for the freeway from Glendale Avenue north to Loop 101.[10] In 1989, the bridge over the Arizona Canal was complete, as well as the overpass at Thomas Road.[8] The southbound Route 51 connector ramp to eastbound Loop 202 and the 20th Street overpass were completed in 1990.[8][11] The city of Phoenix had the freeway completed as far north as Glendale Ave. in 1991.[8] During much of the road's early days in the 1990s, several decorative pots were mounted on top of the noise mitigation walls, which were a source of controversy at the time of their installation due to cost and aesthetics. One resident installed a gold toilet in protest. They were all taken down, however, during the ADOT reconstruction project between McDowell Rd. and Shea Boulevard in 2000.[12]

In 1992, the southern portion was handed over to the Arizona Department of Transportation.[13] Since then, it has been extended to Loop 101 and retrofitted with rubberized asphalt, standardized signage, an additional general purpose lane to create three lanes in each direction, and a high-occupancy vehicle lane up to Loop 101.

In 2007, construction began to widen the Piestewa Freeway between Shea Blvd. and the Loop 101 interchange to include a high occupancy vehicle lane in each direction and on ramps to Loop 101 eastbound. Work was completed in the summer of 2008.[14]

In March 2016, a new interchange from the road's existing terminus at Loop 101 to an intersection with Black Mountain Boulevard opened.[15]

Exit list

Major cross streets of Arizona State Route 51

The entire route is in Phoenix, Maricopa County.


I-10 east – Tucson, Sky Harbor Airport
Southern terminus; exit 147B on I-10

I-10 west / Loop 202 east – Los Angeles
Mini Stack; southbound exit and northbound entrance; exit 147B on I-10; exit 1A on Loop 202

I-10 east
HOV interchange; southbound exit and northbound entrance; exit 147C on I-10
1.101.771McDowell Road
2.113.402Thomas Road / 20th Street
3.175.103Indian School Road
3.926.314AHighland Avenue / Camelback RoadNorthbound exit and southbound entrance
4.437.13Colter Street / Camelback RoadSouthbound exit and northbound entrance; administratively referred to as exit 4B[1]
5.188.344BBethany Home RoadAdministratively referred to as exit 5;[1] exit ramps provide direct access to N. 18th Street (Local traffic)
6.209.985Glendale Avenue / Lincoln DriveAdministratively referred to as exit 6;[1] exit ramps have direct entrance from Ocotillo Road (to NB exit ramp) and Morten Avenue (to SB exit ramp)
7.6412.307Northern Avenue
8.5413.7426th StreetSouthbound entrance only
9.6215.48832nd StreetNorthbound exit and southbound entrance
10.0916.249Shea Boulevard
11.0917.8510Cactus Road
12.1119.4911Thunderbird RoadNorthbound exit and southbound entrance
13.1421.1512Greenway Road
14.1622.7913Bell Road
15.1824.4314Union Hills Drive

Loop 101 east – No access to Tatum Boulevard
HOV interchange; northbound exit and southbound entrance; exit 29B on Loop 101
Loop 101 east
Northbound exit and southbound entrance; exit 29A on Loop 101
Black Mountain BoulevardNorthbound exit and southbound entrance
Loop 101 west
Northern terminus; exit 29 on Loop 101
1.000 mi = 1.609 km; 1.000 km = 0.621 mi


  1. ^ a b c d e Roadway Inventory Management Section, Multimodal Planning Division (December 31, 2013). "2013 State Highway System Log" (PDF). Arizona Department of Transportation. Retrieved January 16, 2016.
  2. ^ a b William Bright, The Sociolinguistics of the 'S- Word' : 'Squaw' in American Placenames, University of Colorado, archived from the original (DOC) on 2010-07-06, retrieved 2009-12-01
  3. ^ a b "Interstate 510". Archived from the original on 27 December 2009. Retrieved 2010-01-11.
  4. ^ Google (2008-08-22). "overview map of SR 51" (Map). Google Maps. Google. Retrieved 2008-08-22.
  5. ^ Arizona Department of Transportation (1968-09-30). "Arizona DOT Right-of-Way Resolution 1968-069". Retrieved 2008-04-14.
  6. ^ Ruelas, Richard (2008-04-24). "Inside the Squaw Peak Storm". The Arizona Republic. Retrieved 2009-12-01.
  7. ^ Williams, Rudi (2003-05-27). "Army Spc. Lori Piestewa – Honoring a Fallen Hero". Armed Forces Press Service. Archived from the original on 2007-08-08.
  8. ^ a b c d e f Arizona Department of Transportation. "Arizona State Highway System Bridge Record" (PDF). Retrieved 2008-04-16.
  9. ^ "SR 51 to I-10 ramp". National Bridge Inventory. Retrieved 2008-04-14.[permanent dead link]
  10. ^ Arizona Department of Transportation (1988-06-17). "Arizona DOT Right-of-Way Resolution 1988-06-A-058". Retrieved 2008-04-14.
  11. ^ "SR 51 to Loop 202 ramp". National Bridge Inventory. Retrieved 2008-04-14.[permanent dead link]
  12. ^ "Fifteen years after the Squaw Peak Pots debacle, the Phoenix art community rallies around a public-art project". Phoenix New Times. Retrieved 2008-04-13.
  13. ^ Arizona Department of Transportation (1992-02-21). "Arizona DOT Right-of-Way Resolution 1992-02-A-012". Retrieved 2008-04-14.
  14. ^ Arizona Department of Transportation. "State Route 51 (Piestewa Freeway)". Retrieved 2008-04-09.
  15. ^ "ADOT, Phoenix open SR 51 ramps at Black Mountain Boulevard". ADOT. Arizona Department of Transportation. March 20, 2016. Retrieved March 24, 2016.
  16. ^ Google (January 16, 2016). "Arizona State Route 51" (Map). Google Maps. Google. Retrieved January 16, 2016.

External links