Extra Space Storage Inc. ("we," "our," "us" or the "Company") is a fully integrated, self-administered and self-managed real estate investment trust ("REIT") formed as a Maryland corporation on April 30, 2004, to own, operate, manage, acquire, develop and redevelop self-storage properties ("stores"). We closed our initial public offering ("IPO") on August 17, 2004. Our common stock is traded on the New York Stock Exchange under the symbol "EXR."
We were formed to continue the business of Extra Space Storage LLC and its subsidiaries, which had engaged in the self-storage business since 1977. These companies were reorganized after the consummation of our IPO and various formation transactions. As of December 31, 2018 we owned and/or operated 1,647 stores in 39 states, Washington, D.C. and Puerto Rico, comprising approximately 125.7 million square feet of net rentable space in approximately 1.2 million units.
Substantially all of our business is conducted through Extra Space Storage LP (the "Operating Partnership"). Our primary assets are general partner and limited partner interests in the Operating Partnership. This structure is commonly referred to as an umbrella partnership REIT, or UPREIT. We have elected to be taxed as a REIT under the Internal Revenue Code of 1986, as amended (the "Internal Revenue Code"). To the extent we continue to qualify as a REIT we will not be subject to U.S. Federal tax, with certain exceptions, on our net taxable income that is distributed to our stockholders.