“Today in 1912 a rural mail carrier in Bennington County, Vermont, used an automobile to carry mail on his route. It was the first use of a car to deliver mail on a rural route.

A rural carrier in Bennington County, VT, was the first to deliver mail by car on a rural route today in 1912.

— Postal Museum (@PostalMuseum) August 7, 2014

Shortly thereafter rural mail might have been delivered in one of these Rural Free Delivery vehicles.” — Smithsonian National Postal Museum  via Facebook and Twitter – August 7, 2014

Here is another picture of rural carrier in automobile