1985 Horses
USPS has printed plenty of images of horses, but all are tied to horse racing or replications of paintings except this series. The four horses pictured here are all breeds specific to the United States, bred from the imports that began arriving to the Americas in the 1500s with Spanish colonists. I used a few from this series for two curated sets within the past week: the two with green lawns for a Kentucky wedding postage set, and the Quarter Horse for a southwestern custom postage set.
These stamps are slightly larger than those printed at the time, measuring 1.5 inches wide and 1.25 inches tall. They were issued in Lexington, KY and 37 million were originally printed.