The Boston and Maine Railroad Extension was incorporated March 16, 1844, due to a dispute with the Boston and Lowell Railroad over trackage rights rates between Wilmington and Boston. That company was merged into the main B&M on March 19, 1845, and opened July 1, leading to the abandonment of the old connection to the B&L (later reused by the B&L for their Wildcat Branch). In 1848 another original section was abandoned, as a new alignment was built from Wilmington north to North Andover, Massachusetts, in order to better serve Lawrence, Massachusetts.