Name four baseball players whose faces have been displayed on U.S. postage stamps.

These four baseball legends were indeed immortalized on U.S. postage stamps, becoming some of the first athletes to receive such an honor. The series of stamps began in 1982 with Jackie Robinson, who was the first baseball player ever featured on a U.S. stamp. This stamp was part of the Black Heritage series, recognizing his monumental role in breaking Major League Baseball's color barrier. The design fittingly captured his famous slide into home plate. The following year, in 1983, Babe Ruth was honored on a 20-cent stamp. Its release was timed to celebrate the 50th anniversary of the first MLB All-Star Game, where the legendary "Sultan of Swat" hit the very first home run.

In 1984, Roberto Clemente was commemorated on a stamp issued in his birthplace of Carolina, Puerto Rico. This stamp, part of the American Sports Series, not only recognized his incredible talent on the field but also his profound humanitarian efforts, which tragically led to his death while on a relief mission. Finally, in 1989, Lou Gehrig, the "Iron Horse," was featured on a stamp released on the 50th anniversary of his retirement from baseball. This tribute honored his remarkable career and raised awareness for the disease that would later bear his name, Amyotrophic Lateral Sclerosis (ALS). In 1989, the U.S. Postal Service also released a "Baseball Legends" scrapbook and stamp album that included these four iconic stamps.