when the maryland state roads commission applied numbers to state highways, they assigned md 170 to its current corridor from severn to brooklyn park and to what is now md 174 from severn to fort meade. the portion of the modern highway from odenton to severn was originally md 554. much of what was to become md 170 was constructed along the old annapolis road between pumphrey and severn. a portion of this road ran through the hamlet of wellham crossroads in the middle of what is now bwi airport. the highway was paved in macadam from the baltimore–annapolis boulevard in pumphrey to hammonds ferry road in linthicum by 1910. a second section of improved highway was planned by 1910 from linthicum south to wellham crossroads. a section of highway from the current md 170–md 174 intersection in severn west to the pennsylvania railroad (now amtrak's northeast corridor) was built as a concrete road by 1915.