Jose "Lil' Moe" Saucedo was one of eight gang members to be charged in the 2014 firebombings of the Ramona Gardens housing complex, but he is the first to be convicted.
Saucedo was sentenced to 13 years, but given 48 months credit for time served on another crime, bringing his sentence to nine years.
The federal indictment alleges the members of the Big Hazard gang were trying to drive black residents out of the housing project amid escalating racial tensions.
The suspects hurled Molotov cocktails at apartments in the complex in May 2014. No one was injured, but homes were damaged, and one firebomb landed near where a woman and her baby had just been sleeping.