A pillbox hat is a small woman’s hat with a flat crown and straight, upright sides.
For example the Jackie O’s pillbox hat – Harry S. Truman Presidential Museum and Library – Independence, Missouri.
Of all the fashion trends set by First Lady Jackie Kennedy, she will be remembered most for her trademark pillbox hat. While Mrs. Kennedy is credited with bringing the hat to the masses, the hat had existed in different forms since the 1930s.
By 1963, interest in wearing the pillbox hat had already begun to fade but came to a sudden halt when Mrs. Kennedy, wearing a pink pillbox hat, cradled the President’s head in her lap after he was struck down by assassin’s bullets.
Rubell's Antiques 
