when the expressway spur between md 168 and u.s. route 301 (now md 648) was built between 1951 and 1954, the expressway, which became part of the baltimore beltway, included an at-grade intersection with md 170 between linthicum and pumphrey. this junction was replaced with the present interchange in 1967; md 170 was expanded to a divided highway on either side of the interchange in 1968. md 170's grade separation with stoney run road on the west side of the airport was built in 1982. the state highway was expanded to a four-lane divided highway from north of i-195 to md 162 when the adjacent east–west portion of md 162 was built in 1988. md 170 was expanded to a four-lane divided highway through its interchange with md 100 when the single-point urban interchange was built in 1995. md 170 had been expanded to four lanes through its interchange with md 32 and from md 176 through the i-195 interchange, and had its southern terminus rolled back from md 677 to md 175, by 1999.