Mark Morton (November 22, 1858 – June 25, 1951) was an American businessman and philanthropist. He co-founded the Morton Salt Company.
He was born in 1858 in Omaha, Nebraska. His father, J. Sterling Morton, was the only territorial governor of Nebraska, a former United States Secretary of Agriculture, and founder of Arbor Day. His mother, Caroline Joy Morton, was the only Caucasian woman present at the signing of the 1854 "Treaty with the Omaha" which paved the way for Nebraska's statehood. He grew up at the family home at Arbor Lodge, and attended public schools in Nebraska City.
At the age of 18, Mark Morton went to work for his older brother, Paul Morton, as a clerk for the Burlington Railroad. In 1882, he became a salesman for the Harvey Lumber Co. of Chicago, and in 1890 was made superintendent of the main plant of the Nebraska City Packing Co. Later in life, he was also president of the Western Cold Storage Company (a major builder and provider of refrigerated storage facilities and railroad cars for the meatpacking industry).
Morton and his second-eldest brother, Joy, were lifelong business partners. In 1885, he and Joy Morton co-founded the Joy Morton Lumber Co. They later co-founded the Morton Sand and Gravel Company.
They purchased Richmond and Company, a salt distributor in 1886 and renamed it Joy Morton and Company. Mark Morton was the company's vice president and one of its directors from its founding until his retirement in 1922. The company became the International Salt Company in 1902. Morton was forced to testify in federal court in 1903 after government investigators accused the company of antitrust violations. The company was incorporated in Illinois as the Morton Salt Company in 1910.