Whittaker was born on a farm near Troy, Kansas to Charles Edward Whittaker, a farmer, and Ida Eve Miller, a schoolteacher from Hagerstown, Maryland.
Whittaker joined the law firm of Watson, Ess, Marshall & Enggas in Kansas City, Missouri, where he previously toiled full-time as an office boy, and built up a practice in corporate law with the Union Pacific Railroad, Montgomery Ward, and the City National Bank and Trust Company among his clients.