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

Ammon
Boise
Caldwell
Dalton Gardens
Eagle
Fruitland
Garden City
Hayden
Idaho Falls
Jerome
Kuna
Lewiston
Meridian
Nampa
Orofino
Pocatello
(no Q)
Rexburg
Sandpoint
Twin Falls
Ucon
Victor
Weiser
(no X)
(no Y)
(no Z)