Pickup trucks are finally getting an official stamp of approval.

The United States Postal Service is issuing new Forever stamps on July 15 adorned with classic American pickups.

The images of the four “rugged and reliable work vehicles,” as the agency calls them, span 27 years of models.

The oldest is the 1938 International Harvester D-2, which was among the first pickups to shift from purely utilitarian design to a more luxurious, stylish look. International Harvester was known for its agricultural equipment, but the D-2 boasted chrome trim in addition to a six-cylinder engine and its ability to carry half a ton of weight.

The 1948 Ford-F1 was the automaker’s first truck produced after World War II. The vehicle had a sizable “Million Dollar Cab” in addition to more sophisticated detailing and suspension. In its first year, it sold more than 300,000 units.

The F-series has been the country’s best-selling truck since 1977 and vehicle of any type since 1982, according to Ford Motor Co.

The 1953 Chevrolet 3100, with its distinctive wavy grille, also stars on the stamps. It’s part of the Advance-Design line, which debuted in 1947 and remained the top-selling pickup in the country for nearly a decade.

Finally, there’s the 1965 Ford F-100. This model had a brand new Twin-I-Beam independent front suspension, which improved ride smoothness and stuck around in some form until 1996. The vehicle also introduced an 18-slot grille.

“We’re proud that two F-Series trucks are featured as part of the USPS tribute to American pickups,” said Ford spokesman Michael Levine.

The USPS has often had wheels on the brain, releasing several series of stamps focusing on vehicles and transportation, according to William J. Gicker, the agency’s creative director and manager of stamp development.

In 2014, the agency issued limited-edition Hot Rods Forever stamps featuring two 1932 Ford “Deuce” roadsters. Earlier, in 2008, USPS celebrated five popular cars from the 1950s. Two years before that, four classic American motorcycles were depicted on stamps.

But the pickup truck stamps are “a rare find,” said Scott D. English, executive director of the American Philatelic Society.

English said he knows of only six truck appearances on U.S. stamps, none of them pickups. The first was a postal mail truck in 1925, and the last was a 1994 stamp featuring a 1930s tractor-trailer.

By comparison, 29 U.S. stamp issues have featured space vehicles, including satellites.

The upcoming truck stamps were designed by Pittsford, N.Y.-based artist Chris Lyons and Alexandria, Va.-based art director Antonio Alcala. Gicker said Lyons was given “quite a bit of flexibility” in choosing the four featured trucks, being told only to look for vehicles in four colors and distinct shapes.

“Our vintage pickup trucks are true Americana and we love them,” Gicker said.

Pickup trucks first emerged in the early 1900s but were common by the Great Depression.

The stamps will be issued as a first-class mail Forever booklet of 20 stamps for $9.40. Forever stamps can be used to mail first-class letters regardless of the current postal rate. Even if the cost of sending a normal 1-oz. letter rises in 2017 or 2027, a Forever stamp purchased in 2016 will still do the trick.