A native of Houston, Texas, and the son of a United States Army physician and nurse, Cappleman was one of eight children raised by his mother after his father's death.

Cappleman ran for alderman of Chicago City Council's 46th ward in 2007, challenging incumbent Helen Shiller and making issues of crime and public safety central to his campaign.

[7] Cappleman was a member of Budget, Ethics, Health, Housing, Licensing & Consumer Protection, Pedestrian & Traffic, and Zoning Committees.

[9] Cappleman worked with Congresswoman Jan Schakowsky to encourage the City of Chicago to create a housing-first pilot project that housed 75 people living under two Uptown viaducts along Lake Shore Drive in 2016.

In May 2017, he was the lead sponsor of a resolution that called for the City of Chicago, Cook County, and the State of Illinois to collaborate to create interventions to reduce prison recidivism, especially among those frequently arrested who have mental illness.