People’s United Financial Inc. has completed its acquisition of LSB Corp., an $800 million bank holding company based in North Andover.

The Bridgeport, Conn.-based bank also completed its purchase of Smithtown Bancorp Inc., a $2.3 billion bank holding company based in Smithtown, N.Y.

LSB Corp.’s subsidiary, River Bank, has seven branches, five of which are just north of Boston and two of which are in southern New Hampshire. Smithtown Bancorp’s subsidiary, Bank of Smithtown, has 30 branches on Long Island and one in New York City.

The LSB Corp. acquisition is an all-cash transaction valued at $94.8 million. The transaction values each LSB Corp. share at $21. LSB shareholders approved the transaction on Oct. 27.

The Smithtown Bancorp Inc. acquisition is valued at approximately $56.4 million, or $3.77 per share, with approximately 53 percent being paid in cash and the balance in the form of shares of People’s United Financial common stock. Smithtown Bancorp shareholders approved the transaction on Nov. 19. The Office of Thrift Supervision, People’s United Bank’s primary regulator, approved the transactions Nov. 15.

"We are pleased to expand the People’s United Bank franchise in the greater Boston and New York markets," said Jack Barnes, president and chief executive officer of People’s United Financial. "The seven former River Bank branches are an excellent fit with our existing footprint in Massachusetts and southern New Hampshire, considering our FDIC-assisted purchase of Butler Bank in Lowell earlier this year, and our two new branches in downtown Boston. The former Bank of Smithtown branches are a natural extension of our Westchester County and Fairfield County markets and an exciting expansion of our franchise into the New York Metro area."