Interstate 170 was a planned spur to the north side of Downtown Baltimore from I-70 in the western portion of the city. Approved by the American Association of State Highway and Transportation Officials (AASHTO) on June 30, 1970, the short section of I-170 was completed in 1979. I-170 was signed along the route until 1983, when U.S. 40 replaced it from adjacent Franklin and Mulberry Streets.
Since Interstate 70 was never constructed in Baltimore, I-170 was never completed to its planned western terminus. A subsequent proposal called for turning the route southward to the planned interchange linking I-70 with Interstate 95 by Carroll Park. Had it been built, the urban loop would have been numbered as Interstate 595.