The electric car pictured on the 4-cent Pan American Issue stamp displayed the real technological advancements being made in the United States. The car was owned and operated by the Baltimore & Ohio Railroad in Washington, D.C., explaining the Capitol building shown in the foreground.
It was the first four-cent stamp printed in more than one color (deep red brown and black). There would not be another multicolored four-cent stamp for over another fifty years. That stamp would be the 4-cent Flag Issue stamp that was released in 1957. The six stamps of the Pan American Issue were the first multicolored stamps since the Pictorial Issue of 1869. And like that Issue, the first three denominations of the Pan American would produce inverts.
The 4-cent stamp typically paid the double two-cent first-class domestic rate; or when used with other denominations, it fulfilled large-weight and foreign destination rates. A total of 5,737,100 stamps were printed by the Bureau of Engraving and Printing.