Here's the rundown on Pizzeria Uno. It was started by a man named Ike Sewell in 1946. Like many soldiers returning from WWII, he acquired a taste for pizza while in Italy during the war. He invented the Chicago style of making the pizza in a high sided pan and putting the sauce on top of the cheese instead of the cheese on the sauce, etc. Uno was so popular, Sewell opened Pizzeria Due a block away from Uno.
Sewell received many offers to buy him out or franchise Uno and he always refused, not believing the quality could be maintained. After Sewell passed away (I think sometime around 1990), his widow kept on running things. Finally, after a few years, she decided to accept one of the offers to sell from a restaurant corporation based in Boston. The Boston corp pledged not to alter the original Uno and Due in Chicago. However, when the Boston corp started opening branches all over the USA, it made the regretable decision to alter the recipe at each location according to "local tastes."
I have eaten at the original Uno and Due since the Boston corp took over and as far as I can tell, they kept their pledge the pizzas tasted right ... at least on the days I've been there. ALL other Uno locations are only loathsome pale shadows of the original Uno pizza.
Some reliable Chicago pizzerias that carry on the tradition of true Chicago pan pizza are Malnati's (started by Lou Malnati, who used to bartend at the original Uno/Due), Giordano's, Gino's, Edwardo's. IMHO, Malnati's comes closest to the original Uno, but all of them are good.