A persistent challenge in computer science (CS) graduate education is the lack of representation, retention, and graduation of certain racial and ethnic groups. Despite increased enrollment in computer science departments across the United States, the persistence of Black/African-American students remains primarily unchanged since the mid-1990s, particularly at the doctoral degree level. The Institute for African-American Mentoring in Computing Sciences (iAAMCS) is an NSF Broadening Participation in Computing Alliance (BPC-A) that provides a national ecosystem by connecting students and faculty through short and long-term programmatic activities to build community and advance Blacks/African-Americans in computing research. This paper presents an analysis of admissions and graduation data of Black/African-American CS PhD students from the CRA Taulbee surveys from 1995 to 2018. The findings suggest that less than 50 percent of the Black/African-American students that enter CS PhD programs finish. However, of those Black/African-American CS PhD students that have engaged in iAAMCS activities, 86 percent completed their PhD.