While originally topped with Velveeta, Altoona-style pizza is popularly topped with yellow processed cheese known as American cheese. The yellow squares of American cheese are a staple of this dish, used instead of the mozzarella or provolone common to other styles of pizza.
Everything about that paragraph makes me feel ill.
Fun fact, you can trigger Wikipedia editors by changing the page in developer console and posting a screenshot of it, they'll scramble to revert a change that doesn't exist.
The most successful businesses in Altoona when I lived there in the early 2010s were drug rehabilitation centers. All the factories closed, and the town is slowly dying.