Lowell is a city in the US Commonwealth of Massachusetts. Located in Middlesex County, Lowell served as a county seat until Massachusetts disbanded county government in 1999. With an estimated population of 109,945 in 2014, it is the fourth-largest city in Massachusetts, and the second-largest in the Boston metropolitan statistical area. The city is also part of a smaller Massachusetts statistical area called Greater Lowell, as well as New England's Merrimack Valley region.