From the LCMS website:
Silas, a leader in the church at Jerusalem, was chosen by Paul (Acts 15:40) to accompany him on his second missionary journey from Antioch to Asia Minor and Macedonia. Silas, also known as Silvanus, was imprisoned with Paul in Philippi and experienced the riots in Thessalonica and Berea. After rejoining Paul in Corinth, he apparently remained there for an extended time. Beyond that there is little further mention of Silas and his association with Paul.