Boston is a city that prides itself on making history. It created a volunteer night watch in 1636 and established a publicly funded police department with full-time officers in 1838. But it took until Monday for Boston to swear in its first African-American police commissioner, William G. Gross, 54.

Who is the new police commissioner?

For the last four and a half years, Mr. Gross (pronounced like toss) has been the superintendent in chief, the second-highest position on the force. Now he is replacing the outgoing commissioner, William B. Evans, who will become the executive director of public safety at Boston College.

Did he grow up in Boston?

As a 12 year old, the new commissioner moved from his grandmother’s farm in rural Maryland to Dorchester, a large, diverse Boston neighborhood. It was 1975, a year after a federal judge ordered the city to desegregate its public schools, a decision that led to violent protests in some predominantly white neighborhoods. Boston became a symbol of northern racism.