1997 $3 Mars Pathfinder
US #3178 measures 3 inches across and 1.5 inches tall.

On December 10, 1997, the USPS issued its largest postage stamp, honoring the Mars Pathfinder.

NASA launched the Mars Pathfinder on December 4, 1996. The spacecraft landed on Mars on July 4, 1997. Over the next few months, the Mars Pathfinder rover moved across the Martian surface analyzing the planet’s atmosphere, climate, geology, and the composition of its rocks and soil. In all, it sent back 2.3 billion bits of data, 16,500 pictures, and took 8.5 million measurements. Pathfinder sent back its last data transmission on September 27, 1997.

1997 $3 Mars Pathfinder Colorano Silk Cachet First Day Cover
US #3178 – Colorano Silk Cachet First Day Cover

To honor this achievement, the USPS planned a special stamp. Issued on December 10, 1997, the Mars Pathfinder Priority Mail stamp was the last stamp issued that year. The stamp pictures the first image sent from the Pathfinder, the remote-controlled vehicle, Sojourner, which collected data about the soil and rocks, with the Mars landscape in the background. The Mars Pathfinder’s robotic rover was named for Sojourner Truth, an abolitionist and women’s rights activist.

1865 5c Newspaper & Periodical Stamp - hard paper, no gum, dark blue
US #PR1 – the first Newspaper & Periodical stamp

Measuring 3 inches across by 1.5 inches high, the Mars Pathfinder stamp is the largest US postage stamp ever issued. (Newspaper and Periodical stamps issued in 1865 were larger.) In addition to being the largest US postage stamp, the Mars Pathfinder stamp has several other interesting features.

1978 13¢ Indian Head Penny
US #1734 – America’s smallest postage stamp

The Pathfinder stamp has special “USA” perforations on the bottom row of perfs. And the vertical perfs extend beyond the stamp to the bottom of the selvage for easier removal of the stamp. Hidden words were incorporated into the design and are visible with a stamp decoder. They read “USPS” and “MARS PATHFINDER • JULY 4, 1997” in alternating lines.

And in case you were curious, the smallest US postage stamp is #1734, the 1978 stamp picturing the Indian Head Penny. It was less than an inch wide!

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