The indigenous peoples of the northern reaches of North America named it. A prospector in the late 19th century then renamed it as a political stunt for McKinley's presidential campaign (McKinley was not yet President), and when he became President, McKinley created a national park around the mountain to cement his name into it and make it official. Up until that moment, it was still called Denali. Apparently, even the Russians called the mountain Denali while the place was theirs.
So yeah. I know who named it. And there has been bipartisan support, as well as support from the people of Alaska, to restore the name for 40 years. Using a legal loophole, congressmen from Ohio have been keeping the name from being changed back.