Look at this Venn diagram.

A, B, and C represent three lists of cities.
The cities in each list share a certain characteristic.

1, 2, and 3 represent the intersections of the lists,
e.g. list 1 contains the names of the cities that are in both A and B.
These intersection lists appear below.

The Lien À Trois is the intersection of all three,
i.e. the only three cities that appear in all three of the original lists.
If you can identify A, B, and C, you have your answer.

    • Atlanta, Georgia
    • Boise, Idaho
    • Boston, Massachusetts
    • Charleston, West Virginia
    • Cheyenne, Wyoming
    • Columbia, South Carolina
    • Columbus, Ohio
    • Denver, Colorado
    • Des Moines, Iowa
    • Honolulu, Hawaii
    • Indianapolis, Indiana
    • Jackson, Mississippi
    • Little Rock, Arkansas
    • Oklahoma City, Oklahoma
    • Phoenix, Arizona
    • Providence, Rhode Island
    • Salt Lake City, Utah
    • Anchorage, Alaska
    • Honolulu, Hawaii
    • Indianapolis, Indiana
    • Minneapolis, Minnesota
    • New York City, New York
    • Newark, New Jersey
    • Oklahoma City, Oklahoma
    • Philadelphia, Pennsylvania
    • Sioux Falls, South Dakota
    • Virginia Beach, Virginia
    • Dover, Delaware
    • Honolulu, Hawaii
    • Indianapolis, Indiana
    • Oklahoma City, Oklahoma

(Click on "LAT" in the Venn diagram to go to the answer.)