The Oregon Trail Memorial half dollar was a fifty-cent piece struck intermittently by the United States Bureau of the Mint between 1926 and 1939. The coin was designed by Laura Gardin Fraser and James Earle Fraser, and commemorates those who traveled the Oregon Trail and settled the Pacific Coast of the United States in the mid-19th century. Struck over a lengthy period in small numbers per year, the many varieties produced came to be considered a ripoff by coin collectors, and led to the end, for the time, of the commemorative coin series.

Ohio-born Ezra Meeker had traveled the Trail with his family in 1852 and spent the final two decades of his long life before his death in 1928 publicizing the Oregon Trail, that it should not be forgotten. In 1926, at age 95, he appeared before a Senate committee, requesting that the government issue a commemorative coin that could be sold to raise money for markers to show where the Trail had been. The coin had originally been thought of by Idahoans, led by Dr. Minnie Howard, seeking to further preservation work at Fort Hall; Meeker broadened the idea. Congress authorized six million half dollars, and placed no restriction on when or at what mint the coins would be struck. Meeker's Oregon Trail Memorial Association (OTMA) had tens of thousands of pieces struck in 1926 and 1928, and did not sell them all. Nevertheless, most years between 1933 and 1939, it had small quantities of the half dollar coined, in some years from all three operating mints to produce mintmarked varieties, and raised prices considerably.

Collectors complained that some of the issues were controlled by coin dealers, and individual collectors had to pay high prices. Public protests followed, and in 1939 Congress ended the series. Despite the complaints, the OTMA had difficulty in selling the coins, and they remained available from the OTMA's successor organization as late as 1953. Just over 260,000 of the 6,000,000 authorized coins were struck, of which about 60,000 were melted. The US commemorative coin struck over the longest period, the Oregon Trail Memorial half dollar has been widely praised for its design.

In the middle years of the 19th century, before the completion of the transcontinental railroad in 1869 made travel easier, hundreds of thousands of people journeyed along the Oregon Trail to settle the Far West of the United States. Not all who began the journey reached their destination as there was much suffering and death along the way—by one estimate, 20,000 people lie in unmarked graves.

Ohio-born farmer Ezra Meeker (1830–1928) traveled the Oregon Trail in 1852; he and his young wife and infant child went by ox-drawn wagon from Iowa to Oregon Territory. In his old age, he came to believe that the Oregon Trail, and the sacrifice of those who had died along it, were being forgotten. Amid considerable publicity as one of the last survivors of the pioneers who had blazed the way west, Meeker retraced his route along the Trail between 1906 and 1908. The Trail had in some places disappeared, swallowed up by town and farm, and in his journeys, he sought to find where he had passed, seeking to have historical markers erected. He took his ox team and wagon across the nation to publicize his cause, parking his rig in front of the White House where he met President Theodore Roosevelt. In New York, he crossed the Brooklyn Bridge. In 1910, he and his oxen participated in the Tournament of Roses Parade in Pasadena. In the succeeding years, he traveled the route by oxcart, automobile, and, at age 93 in 1924, airplane, attempting to further his cause, and seeking federal recognition and funding for his efforts.

The Oregon Trail Memorial half dollar stemmed from various efforts by Idahoans who favored the preservation of the site of Fort Hall, an important way station on the Trail. The idea was sparked by the issuance of the 1925 Stone Mountain Memorial half dollar, which caused Mabel Murphy, wife of an Idaho newspaperman, to propose to her husband the striking of an Oregon Trail coin, the profits from which could be used for historic preservation. Her husband, D.T. Murphy, on April 16, 1925, dutifully published an editorial, "Oregon Trail Covered Wagon Half Dollars" in the Idaho State Journal. Mrs. Murphy would not live to see the coin issued, dying November 30, 1925, of tuberculosis.

The idea for the coin was brought up again when civic activists in Pocatello, Idaho, led by Dr. Minnie Howard, sought ideas for funding a monument on the site of Fort Hall. Insurance salesman F.C. McGowan displayed a Stone Mountain piece, "Yes. Coinage. Like this!" Howard and her colleagues pursued the idea. Meeker did as well once he heard of it, forming the Oregon Trail Memorial Association, ("OTMA" or "the Association") a national organization, which could also receive the half dollars, and sell them at a profit.

An act to authorize the coinage of 50-cent pieces in commemoration of the heroism of the fathers and mothers who traversed the Oregon Trail to the far West with great hardship, daring, and loss of life, which not only resulted in adding new states to the Union but earned a well-deserved and imperishable fame for the pioneers; to honor the twenty thousand dead that lie buried in unknown graves along two thousand miles of that great highway of history; to rescue the various important points along the old trail from oblivion; and to commemorate by suitable monuments, memorial or otherwise, the tragic events associated with that emigration—erecting them either along the trail itself or elsewhere, in localities appropriate for the purpose, including the city of Washington.