The community known as King of Prussia, Pennsylvania was named after a local 18th century tavern. It had taken its name from King Frederick II (a.k.a. Frederick The Great) of Prussia, a former German state.
Image from Wikipedia / Anton Graff

In 1963, KING OF PRUSSIA PLAZA housed tenants such as a Korvettes discount mart, F.W. Woolworth and prototype, full-line J.C. Penney. The complex spanned around 700,000 leasable square feet, with an eventual fifty stores and services. Free parking was provided for 9,000 autos. One might notice that the designations of two adjacent Interstate highways are different than they are today. These roadways would be renumbered in February 1964.

KING OF PRUSSIA PLAZA TENANTS 1963:

E.J. KORVETTE (with attached Furniture & Carpet Center, Fashion Show Salon International and freestanding Tire Center) / J.C. PENNEY (with Minute Man Snack Bar, beauty salon, optical department and portrait studio) / ACME MARKETS / F.W. WOOLWORTH 5 & 10 (with freestanding Harvest House Restaurant and Kiosk Snack Shop) / THRIFT DRUG (with luncheonette) / Adams Clothes For Men & Boy's / Baker's Shoes / Brooks Sporting Goods / Country Flair, Limited ladies' wear / Cutler Paints / Dial Shoes / Fashion Bug ladies' wear / Flagg Brothers Shoes / Horn & Hardart Retail Store / Household Finance Corporation / Jackman's men's wear / Junior Shoe World / King's Max For Snax / Maffel Beauty Shop / Marlboro Book Store / Marianne Shops ladies' wear / Marquetland's Candies / Mila Fabrics / Miles Shoes / Mincarelli Barbers / Norge Cleaning Village laundromat / Philadelphia National Bank / Philadelphia Saving Fund Society / Provident Tradesmens Bank / Quaker City Federal Bank / Ritchey Gift Shop / Schearer Florist / Singer Sewing Center / Stephensons Studios Photographers / William A. Schwartz, Optician / Wurlitzer Music Company