Dewey–Humboldt was incorporated on December 20, 2004, from the existing unincorporated towns of Dewey and Humboldt, located adjacent to one another in the Agua Fria River Valley, 15 miles east of Prescott.

During 1864, he led the storied Woolsey Expeditions to the east in retaliatory raids on Apache and in search of gold; all failed to find a new Eldorado.

(The ruins of Woolsey's ranch house can still be seen between the old Black Canyon Highway and the Agua Fria River about one mile north of Humboldt.

The stage station (Prescott to Phoenix wagon road via Black Canyon) and post office nearby was named "Agua Fria."

The small plant, built at the site of Woolsey's earlier mill at today's Humboldt, proved the value of the region, but was too isolated to make a profit.

The Val Verde post office was renamed Humboldt in 1905 to honor Baron Alexander von Humboldt, who had visited New Spain early in the 19th century and predicted that greater riches would be found to the north (interpreted by early twentieth century promoters as the Bradshaw Mountains region).

With two daily trains, business in the town boomed and the city decided to showcase their development by hosting a Labor Day celebration that year.

The celebration featuring a parade on Main Street became an annual tradition, now organized by the Agua Fria Chamber of Commerce and held on the last Saturday in September.

Humboldt had a second but smaller boom in 1934 when the mine reopened, but its duration of operation would be longer under the Shattuck-Denn company of Bisbee, Arizona fame.

The Iron King became the most productive mine in the Bradshaws, and produced $100 million in gold, silver, lead and zinc before its closure in 1968.

You can eat them and they'll pass right through you," said Rob Morgan, Ironite's executive vice president and chief operating officer.

"[9] However, the United States Environmental Protection Agency has recently posted a cautionary statement, warning that potentially harmful amounts of arsenic could be released from use of Ironite.

Today in Humboldt, a lone smelter smokestack, a significant reminder of the region's mining history and pioneers' legacy, remains overlooking the historic buildings on Main Street.

[15] King S. Woolsey was a notable American pioneer rancher, Indian-fighter, prospector and politician who had a ranch located right off the Old Black Canyon Highway in what is now the town of Dewey-Humboldt.

Hay rides, pumpkin patches, and a country restaurant made it a popular attraction for city dwellers seeking a taste of farm life.

Youngs Farm held a "Pumpkin Fest" every October, drawing large numbers of tourists from other parts of Arizona.