If you blink, you might miss the Canyon Padre Bridge in Coconino County. But this unassuming structure was once a very important part of transportation on Route 66, about 22 miles east of Flagstaff.

The Canyon Padre wasn't very deep or wide, but it was a major problem for traffic on the new Santa Fe Highway. In 1913, state engineer Lamar Cobb decided to build a bridge across the canyon. After a bid was accepted and construction began, the bridge was completed in April 1914.

It's true that the tightly-curved approaches to the bridge were dangerous... and yet, the Canyon Padre Bridge carried mainline traffic on the Santa Fe Highway for more than 20 years until its replacement in 1937. It now carries some local traffic on the Navajo reservation.

This bridge is notable for being Arizona' first Luten (or horseshoe) arch, a patented bridge design only used in around 4,000 bridges nationwide. It's also one of the few still-intact portions of the Santa Fe Highway (or National Old Trails Highway). The highway was rerouted before it was paved along this stretch, leaving the road and bridge in basically original condition.

Seeing this bridge today, you get a very good idea of what it was like to travel our state's highways in the 1920s and 1930s.

The town of Winkelman, on the border of Pinal and Gila counties, has a distinctive bridge claim to fame.

The Winkelman Bridge began life back in 1915, when the Pinal County Board of Supervisors appropriated $52,000 from a $500,000 bond issue to build it. Because Winkelman is located on the border of Pinal and Gila counties, Gila County agreed to pay half of the construction cost. At the advice of Assistant State Engineer T.M. Nichols, the structure would be built using multiple-span concrete arches.

In August 1915, R.V. Leeson, assistant engineer for the National Bridge Company, completed the drawings. As delineated by Leeson, the  structural type that would be use had been patented by Daniel Luten, with its distinctive horseshoe-arch profile.

In the fall of 1915, the construction bid was awarded to a Kansas company, Topeka Bridge & Iron Company, which finished the structure in November 1916. It's carried only local traffic since the construction of SR 177. In 1999 the Winkelman Bridge was restored with replicas of the original guardrails and is now a pedestrian-only structure.

The Superior-Mammoth Road was, for decades, an important route in Pinal County. The Winkelman Bridge is an important remnant of that route. In addition, the bridge is a great early example of the multiple-span Luten high arch and one of only 13 identified in Arizona that use these arches.

They say it’s a good idea not to burn your bridges, and I’m inclined to agree. But if you’re going to replace it with a brand-spanking new bridge, then why not?

Another new bridge replaced an older one in the A-1 Mountain Road overpass over I-40 in west Flagstaff. Using innovative construction methods, ADOT was able to demolish and replace the bridge in less than 40 days.

In fact, new bridges have been popping up all over northern Arizona. The A-1 Mountain Road Bridge joins these new bridges that were built in the last few years:

• Rio de Flag Bridge in downtown Flagstaff
• I-40 bridges over Business 40 in west Flagstaff
• Fourth Street Bridge in east Flagstaff
• Meteor City Road Bridges near Meteor Crater
• I-40 Hughes Avenue Bridge to Bellemont

Many of these bridges were replaced using time-saving techniques that cut down on traffic impacts, like precasting bridge elements off-site, the bridge-slide method and geosynthetic reinforced soil-integrated bridge system. 

Have gone a bridge too far?

Just wait as ADOT continues to work on replacing the I-40 bridges at Pineveta Draw near Ash Fork, the I-15 Virgin River Bridge No. 1 in the northwest corner of Arizona and the Lukachukai and Agua Sal North bridges along US 191 in the Navajo community of Round Rock.

ADOT is also rehabilitating bridges along I-40 at Hermosa Drive in Holbrook, Seligman at Exit 123 and Anvil Rock Road 11 miles west of Seligman. 

Check out more bridge content on our website.

"The spandrel of an arch bridge is the area between the arch ring and the roadway. ... Open-spandrel arches have columns resting on the arch ring that support floor beams, which in turn carry the roadway."

We know what you're thinking: Uh, OK, what does that mean in plain English? Let's show you an example: Cienega Creek Bridge in Pima County.

Known as Arizona's longest open-spandrel bridge, the Arizona Highway Department -- a precursor to the Arizona Department of Transportation -- began construction of Cienega Creek Bridge began in 1920 as part of the new Borderland Highway (US 80) across southern Arizona. The bridge is located a few miles east of Vail, Ariz., and near a railroad.

Construction was finished in 1921. At 146 feet, Cienega Creek Bridge's open-spandrel arch is comprised of two tapered ribs that are anchored in concrete foundations with spread footings. 

The bridge was part of U.S. 80 from 1926 to 1955 and was put on the National Register of Historic Places in 1988. It is no longer a state highway and, today, carries local traffic on Marsh Station Road.