From the wikipedia: "White Tower Hamburgers was founded in 1926 in Milwaukee, Wisconsin, and with its similar white fortress-like structure, is considered an imitator of White Castle." The chain expanded to other cities, including Chicago, Indianapolis, Cleveland, Detroit,
Philadelphia, Pittsburgh, New York City, Albany, Boston, and south to Richmond. "During the Great Depression, White Tower sold hamburgers for five cents."

"The whiteness of the restaurant was meant among other things to evoke hygienic conditions, and the chain had staff dressed as nurses, dubbed the "Towerettes," to help make this argument."