CoreSite Realty Corporation is a real estate investment trust that invests in carrier-neutral data centers and provides colocation and peering services.

As of December 31, 2016, the company owned 20 operating data center facilities in 8 markets comprising over 3.5 million net rentable square feet. The properties are in Boston, Chicago, Denver, Los Angeles, Miami, New York City, Northern Virginia, San Francisco/San Jose, California, Santa Clara, California, and the Washington DC areas.

The company has over 1,000 customers including enterprises, network operators, cloud providers, and supporting service providers.

The company was founded in 2001 as CRG West at two of the West coast's original carrier hotels: Market Post Tower and One Wilshire.

In August 2005, the company opened a facility in Washington, D.C.

In May 2007, the company acquired properties in Boston and Chicago.

In September 2007, the company announced the expansion of services at its Los Angeles facility.

In November 2007, the company announced the expansion of services at its Miami facility.

In January 2008, the company acquired a data center in Reston, Virginia.

In June 2009, the company changed its name to CoreSite.

In September 2010, the company became a public company via an initial public offering.

In April 2012, the company acquired Comfluent and entered the Denver market.

In May 2016, The Carlyle Group reduced its effective interest in the company to 28.9%.

In July 2016, Tom Ray, the chief executive officer of the company, retired.

In August 2016, the company announced the expansion of services at its Reston, Virginia facility in conjunction with the $60 million acquisition of the 22-acre Sunrise Technology Park from Brookfield Office Properties.

In February 2017, the company announced the expansion of services at its Washington, D.C. facility.