Illinois-based drugstore chain serves neighborhoods with fully stocked stores and modern amenities.. In Short Founded in 1901 in Chicago by Charles R. Walgreen Sr., this neighborhood pharmacy has grown to be one of the nation's largest drugstore chains. Each store carries 25,000 different items--from cleaning products to electronics and greeting cards. Store features include a computerized system connecting pharmacies nationwide via satellite, grocery-store food aisles, one-hour photofinishing and an automated phone system for prescription refills and pre-arranged pickup times. Other services include in-store flu shots and childhood immunizations.