As president of the Council in 1945, Kerrigan became acting Mayor of Boston upon the inauguration of Maurice J. Tobin, who had been mayor since 1938, as governor. His mayoralty was defined by shortages and debt due to the postwar climate. He passed a bill that saved Boston taxpayers approximately $12 million over the next 20 years by refinancing the bonded debt from the
Sumner Tunnel. He also was able to increase the city's income by leasing the Houghton & Dutton department store on
Tremont Street to the federal government. He promoted many long-term construction programs to spur growth within the city. Kerrigan served as acting mayor in January 1946, until Curley was inaugurated. == Retirement and death ==