MD 140 passes through the northern part of central Maryland, connecting Baltimore, Pikesville, Reisterstown, Westminster, Taneytown, and Emmitsburg.

The remaining portions of MD 140 between its southern terminus in Baltimore and I-795 are classified as National Highway System principal arterials.

The route reaches a four-way intersection with Pennsylvania Avenue and Reisterstown Road, which head southeast and northwest, respectively.

The highway passes along the southwest side of the Parkview/Woodbrook neighborhood and intersects Gwynns Falls Parkway just before Monroe Avenue splits off as a one-lane ramp from southbound Reisterstown Road.

One block north of the convergence of the one-way pair, the state highway intersects Liberty Heights Avenue, which heads west as MD 26, on the east side of Mondawmin Mall.

MD 140 passes the Louisa May Alcott School and enters Central Park Heights, where the state highway intersects Cold Spring Lane before veering west along the northern edge of the Towanda-Grantley and Lucille Park neighborhoods and the southern edge of Langston Hughes neighborhood.

The highway intersects Northern Parkway and passes between the neighborhoods of Glen to the northeast and Reisterstown Station on the southwest.

MD 140 passes along the edge of the Falstaff neighborhood before leaving the city of Baltimore south of Seven Mile Lane.

The ramps merge and MD 140 continues northwest as a four-lane divided highway with a narrow median.

The two highways pass the TownMall of Westminster just east of their partial cloverleaf interchange with MD 27 (Manchester Road), just west of which they cross over the Maryland Midland Railway.

MD 140 continues west as four-lane College View Boulevard, which becomes undivided three-lane (one lane westbound, two lanes eastbound) Taneytown Pike at its intersection with the northern end of MD 31 (New Windsor Road), which provides access to McDaniel College.

At Meadow Brook Farm and Roop's Mill on the western edge of the city of Westminster, the highway crosses Meadow Branch of Big Pipe Creek and has an intersection with Hughes Shop Road and the eastern end of MD 832 (Old Taneytown Road).

Antrim Boulevard forms the southwest leg of the roundabout and MD 140 continues northwest along Baltimore Street into the Taneytown Historic District.

MD 140 leaves the town and gains the name Waynesboro Pike for the short distance northwest to the Pennsylvania state line.