For Miley, who was first elected to the county board in November 2000 and now also represents Pleasanton, it was also his last day to serve as president of the board, a board-elected position that changes each year.
Bishop Bob Jackson of Acts Full Gospel Church in Oakland officiated at Monday's ceremony.
Miley was re-elected in 2004 and 2008, and won 70% of the votes cast in the 2012 election. Prior to representing District 4, he was a member of the Oakland City Council, serving its District 6, a position he won in a 1990 municipal election.
After finishing law school at the University of Maryland in 1976, Miley moved to Oakland to work as a Jesuit volunteer. He began his community involvement by working with numerous community-based groups as well as training community organizers through the National Center for Urban Ethnic Affairs.
The father of two children, he has lived in Oakland for more than 30 years.
District 4, which he represents, continues to include a part of Oakland and the unincorporated communities of Fairview, Ashland, Castro Valley and Cherryland in addition to the city of Pleasanton.