MD 151 was originally assigned only to Sparrows Point Road, which was improved as a concrete road from the southern end of the highway at the Bethlehem Steel complex to North Point Road in Edgemere by 1921. North Point Road was also built as a concrete road from Edgemere to the North Point are of Dundalk by 1921. That highway, which was designated MD 20 in 1927, was extended south toward Fort Howard and north from North Point to US 40 in Baltimore in 1923. By 1934, heavy traffic between Baltimore and Sparrows Point led the Maryland State Roads Commission to recommend MD 151 and MD 20 from Sparrows Point to Baltimore be expanded from in width.
