The merger of Eastern Bank with MASSBANK was completed over the long weekend.

The merger included converting 44,000 former MASSBANK customer accounts to Eastern and changing signs, fixtures and computer systems in 15 branches across Middlesex County. The merger gives Eastern almost 90 branch locations and more than 100 ATMs across eastern Massachusetts.

This represents Eastern’s third merger in the past four years.

On Sept. 3, Eastern acquired MASSBANK Corp. in a cash transaction valued at $170 million. The acquisition created a $7.1 billion commercial bank serving more than 500,000 consumers and businesses across eastern Massachusetts. Eastern is now one of the largest mutually owned banks in the country, according to the bank.