Organization Corporate Office Properties Trust (COPT) and subsidiaries (collectively, the Company) is a fully-integrated and self-managed real estate investment trust (REIT). Corporate Office Properties, L.P. (COPLP) and subsidiaries (collectively, the Operating Partnership) is the entity through which COPT, the sole general partner of COPLP, conducts almost all of its operations and owns almost all of its assets. Unless otherwise expressly stated or the context otherwise requires, we, us and our as used herein refer to each of the Company and the Operating Partnership. We own, manage, lease, develop and selectively acquire office and data center properties. The majority of our portfolio is in locations that support the United States Government and its contractors, most of whom are engaged in national security, defense and information technology (IT) related activities servicing what we believe are growing, durable, priority missions (Defense/IT Locations). We also own a portfolio of office properties located in select urban/urban-like submarkets in the Greater Washington, DC/Baltimore region with durable Class-A office fundamentals and characteristics (Regional Office). As of March 31, 2019 , our properties included the following:  165 properties totaling 18.3 million square feet comprised of 15.2 million square feet in 146 office properties and 3.1 million square feet in 19 single-tenant data center shell properties (data center shells). We owned six of these data center shells through an unconsolidated real estate joint venture;  a wholesale data center with a critical load of 19.25 megawatts;  15 properties under construction or redevelopment ( ten office properties and five data center shells) that we estimate will total approximately 2.0 million square feet upon completion, including two partially-operational properties; and  approximately 900 acres of land controlled for future development that we believe could be developed into approximately 11.6 million square feet and 150 acres of other land. COPLP owns real estate directly and through subsidiary partnerships and limited liability companies (LLCs). In addition to owning real estate, COPLP also owns subsidiaries that provide real estate services such as property management and construction and development services primarily for our properties but also for third parties. Some of these services are performed by a taxable REIT subsidiary (TRS). Equity interests in COPLP are in the form of common and preferred units. As of March 31, 2019 , COPT owned 98.6% of the outstanding COPLP common units (common units); the remaining common units and all of the outstanding COPLP preferred units (preferred units) were owned by third parties. Common units not owned by COPT carry certain redemption rights. The number of common units owned by COPT is equivalent to the number of outstanding common shares of beneficial interest (common shares) of COPT, and the entitlement of common units to quarterly distributions and payments in liquidation is substantially the same as those of COPT common shareholders. However, COPLPs common units include a special class of unit referred to as profit interest units (PIUs) originating from certain share-based compensation awards issued to executives (described further in Note 15) that are subject to vesting and certain tax event criteria, and accordingly may carry different rights to redemption and distributions than non-PIU common units. COPTs common shares are publicly traded on the New York Stock Exchange (NYSE) under the ticker symbol OFC. Because COPLP is managed by COPT, and COPT conducts substantially all of its operations through COPLP, we refer to COPTs executive officers as COPLPs executive officers; similarly, although COPLP does not have a board of trustees, we refer to COPTs Board of Trustees as COPLPs Board of Trustees.