First, I identified what cities make up the Washington DC metropolitan area: Washington, D.C.; Arlington, Virginia; Alexandria, Virginia; Bethesda, Maryland; Fairfax, Virginia; Frederick, Maryland; Gaithersburg, Maryland; Reston, Virginia; Rockville, Maryland; Silver Spring, Maryland [https://en.wikipedia.org/wiki/Washington_metropolitan_area/ (Principal Cities of the Washington DC Metropolitan Area)].
Second, I identified what universities are in the Washington DC metropolitan area through searching on Google: Washington DC metro universities. Through this search, I found that the following universities are located in Washington DC metro area [https://en.wikipedia.org/wiki/List_of_colleges_and_universities_in_Washington,_D.C.#Institutions/ (Listed hereActive Universities in the Washington DC Metropolitan Area)]. Then, I searched on Google, search queries with the following format: [Washington DC metro university] AND incubat*. I then recorded any incubators that I found through these queries.