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Vivmark Residential, formerly known as Equity Residential, is a real estate investment trust (REIT) based in Arlington, Virginia, and Chicago, Illinois, that stands as the largest owner of apartments in the United States. As of August 2026, the company holds investments in 184,000 rental apartments and has over 11,100 units under construction. Founded in 1969 by legendary investor Sam Zell, the company went public in 1993 with 22,000 units and rapidly expanded through massive acquisitions in the 1990s, including Merry Land and Lexford Residential. In August 2026, the company dramatically transformed by acquiring AvalonBay Communities and changing its name to Vivmark Residential. The company has also faced significant legal scrutiny, agreeing to pay $43 million to over 200,000 California tenants for excessive late fees and $56 million to settle allegations of conspiring with other landlords to use RealPage software to coordinate rent increases.