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

Austin, Texas  
Boston, Massachusetts
Chicago, Illinois
Dallas, Texas
El Paso, Texas
Fort Worth, Texas
Greensboro, North Carolina
Houston, Texas
Indianapolis, Indiana
Jacksonville, Florida
Kansas City, Missouri
Los Angeles, California
Memphis, Tennessee
New York City, New York
Oklahoma City, Oklahoma
Philadelphia, Pennsylvania
Quincy, Massachusetts
Raleigh, North Carolina
San Antonio, Texas
Tucson, Arizona
Upland, California
Virginia Beach, Virginia
Winston-Salem, North Carolina
Xenia, Ohio
Yonkers, New York
Zanesville, Ohio