Yes, it was, although there was quite an argument about it that continues to this day. No one in the state of Alaska calls it "Mt. McKinley", they call it by it's Native American name, "Denali".
William dickey was digging for gold in the sands of the Susitna river and he wrote, after his return to the lower states, an account in the New York Sun “We named our great peak Mount McKinley,...