If the atmosphere was the United States here's how it would break down:
Thor, Iowa is Hydrogen. Thor is the birthplace of John K. Hanson, founder of Winnebago. 179 people.
Florence, South Dakota is Krypton. 371 people.
Butterfield, Minnesota (home of the Butterfield Steam and Gas Engine Show) is Methane, 586 people.
Lewisport, Kentucky is Helium. Abraham Lincoln was unsuccessfully tried for operating a ferry without a license here in 1827. 1,706 people.
Maquoketa, Iowa is Neon. As of the time of writing Maquoketa Caves State Park is closed for bat hibernation. 5,921 people.
Gainesville, Florida is Carbon Dioxide. It's ranked by the National Coalition for the Homeless as the 5th meanest city. 132,567 people.
Chicago, Corpus Christi and Kimball, West Virginia make up Argon. 3,042,217 people total.
All that adds up to around 1% of the atmosphere, mostly Argon.
Oxygen is about 20%, that's California, New York, Oregon, Louisiana, Lake Station, Indiana and Cedar, Kansas. 68,225,139 people.
If you're not listed then you are Nitrogen. Close to 80% at 254,334,562 people.
(Population figures from the US Census 2017 estimates. Atmosphere composition from Wikipedia. Water vapor not included.)