Depending on what you mean by major city , here are several possibilities, including the number of miles from the center of Yellowstone N.P.:Those having an airport with scheduled commercial passenger flights are: JAC: Jackson, Wyoming, 75 miles S BZN: Bozeman Gallatin Field, Montana: 87 miles NNW IDA: Idaho Falls Fanning, Idaho: 104 miles SW BIL: Billings, Montana: 130 miles NE. This is the 248th largest U.S. city at 103,994 people HLN: Helena, Montana: 156 miles NNW GTF: Great Falls, Idaho: 204 miles N SLC: Salt Lake City, 272 miles SSW. This is the 126th largest U.S. city at 181,698 peopleThose closest city among the 100 largest U.S. cities is Boise, Idaho, 288 miles WSW at number 100 with 205,314 people.
As you see, there are no major towns near Yellowstone, but i thought you might like to know about the towns that ARE there.
Depends upon what you call major. Idaho Falls ID is about 155 miles from Yellowstone. It has a mall. The nearest city with over a million residents is Denver CO, about 580 miles from Yellowstone.