Mason B. Flagg, 77, of Cheyenne died March 31, 2015 at Cheyenne Regional Medical Center. He was born November 17, 1937 to Louis and Hazel Flagg in Lowell, MA, then moved to Wyoming and grew to love his adopted home. He married Karen Owen on September 18, 1997 in Cheyenne. He was an executive director of the Association of American Railroads, and was a member of the National Railway Historic Society and the American Legion Post #6. He is survived by his wife, Karen Flagg of Cheyenne; children, Susan Flagg (Mark) Stewart of Kettering, OH, Lori (Rich) Reynolds of New Greenwich, RI and Kenneth Flagg of Lowell, MA; stepdaughters, JoAnn Ives of Redlands, CA and Janet (Kirk) Sprague of Champion, NE; grandchildren, Benjamin William Bancroft Riches (Rebecca Courtney), Jennifer Ella Noel Riches (James Viets), Mary Reynolds, Evan Reynolds, Adam Flagg, Beth Flagg and Eric Flagg. He was preceded in death by his parents. In lieu of flowers donations may be made to the charity of your choice. Private family services will be held in Kennebunkport, ME. Cremation has taken place under the care of Schrader Funeral Home.