At least three, apparently. These are historical museums, which, the East Valley Tribune says, are undergoing some philosophical changes, though what those changes might be aren’t really spelled out:

Museums of history have suffered more than science or other kinds in recent years as technology and interactive experiences have transformed nearly every aspect of society and made history seem dull.

Museum operators say East Valley history museums will change significantly with more interactive displays and more traveling exhibits. A new museum planned in downtown Chandler signifies what most museums are trying to become. The city is planning a 25,000 square foot building downtown that is seen as the anchor of the arts and culture district. It would feature gathering places for speakers and performances amidst displays that would change frequently so visitors would have a reason to return frequently.

Turns out Mesa and Tempe already have their own local historical museums, though why they exist is a little unclear; even the Phoenix Museum of History at Heritage Square shut down last summer.