He attended Hanover College, where he became a member of the Sigma Chi fraternity, before graduating from Murray State University in 1966.
Following graduation Armstrong worked in the public and private sector, including a term as a family court judge and election as Jefferson County's Commonwealth's Attorney, the local felony prosecutor.
The city of Louisville was merged with Jefferson County near the end of his term; Armstrong was a supporter of the ballot measure that brought about the merger.
Nevertheless, some, including members of the city's NBA pursuit team, blamed Armstrong for a lack of leadership on the issue.
The firing won praise from the African American community, but enraged police officers and supporters, leading to a march on Louisville City Hall.