The firm has purchased all of the publicly held shares of common stock of State Auto Financial at $52 apiece.
Liberty Mutual added premium of $2.3bn through the merger deal, which was signed in July 2021.
Based in Columbus, Ohio, State Auto Group is engaged in distributing personal and small commercial coverages in 33 US states.
With around 3,400 independent agents, the firm employs more than 2,000 people who will now be part of Liberty Mutual’s Global Retail Markets US business unit.
Upon completion of transaction, State Automobile Mutual Insurance Company members are now mutual members of Liberty Mutual Holding Company Inc.
Throughout most of this year, the firms will continue to run as separate entities.
Liberty Mutual Global Retail Markets US president and COO Hamid Mirza said: “Across Liberty Mutual and State Auto, we have a shared commitment to the Independent Agency channel and being the carrier of choice for independent agents.
“Together, we’ll be a leader in both the personal lines and small commercial insurance markets, helping policyholders when they need it most and giving our people more opportunities to grow and thrive.”
Furthermore, Liberty Mutual named Kim Garland as the president of State Auto.
Garland said: “Our combined strength allows us to significantly expand our relationships with independent agents and brokers, and make more strategic investments in the independent agent channel to continue driving profitable growth.”
The deal makes Liberty Mutual the second-largest carrier in this key distribution channel.