The alphamegalog of the cities of Oklahoma lists the largest city in Oklahoma for each letter of the alphabet. In this case, ‘largest’ is based on population within the city proper.

Ardmore
Broken Arrow
Claremore
Duncan
Edmond
Fort Gibson
Guymon
Henrietta
Idabel
Jenks
Kingfisher
Lawton
Moore
Norman
Oklahoma City
Ponca City
Quinton
Roland
Stillwater
Tulsa
Union City
Vinita
Woodward
(no X)
Yukon
Zeb