The road started on the B1200 Westgate and headed east along St Mary's Lane to end after less than half a mile on the B1520 Grimsby Road.
St Mary's Lane was originally unclassified then became the A1097 in 1926. It is possible it later became a spur of the A157. The road was downgraded to Class II status in the early 1990s following construction of the A16 Louth bypass and became the B1521. However, the road is now mapped as a spur of the B1200, suggesting that the B1521 number was short-lived.