Peoria, AZ home search page was created with you in mind. Peoria is a rapidly growing suburban community. Formerly an agricultural town, today it is a business and medical hub for the Northwest Valley area. It is bordered on the west by Sun City, on the east by Phoenix and Glendale, and on the north by Yavapai County. Peoria was settled in the 1880s when families from Peoria, Illinois, took up residence and began farming. The first post office in Peoria opened in 1888. Over the years, the number of farms increased and the town settled into a quiet rural lifestyle. Peoria began to change in the 1960s when the retirement community of Sun City opened. From 1980 to 1990, the city experienced phenomenal growth, with population increasing 300 percent.