Mack-Cali Realty is a real estate investment trust that owns and operates office, flex, industrial, and multifamily properties in the Northeastern United States. The vast majority of the company's real estate portfolio is split between office buildings and flex facilities, which are buildings that combine warehouse and office space into one location. Mack-Cali primarily derives its revenue as rental income from tenants. The urban and suburban real estate markets of Jersey City, New Jersey; Newark, New Jersey; Westchester-Rockland, New York; and Bergen-Passaic, New Jersey generate most of the company's total revenue. Mack-Cali's largest tenants include a variety of financial, insurance, manufacturing, and legal services firms.