U.S. Route 40 | ||||
|---|---|---|---|---|
 US 40 highlighted in red | ||||
| Route information | ||||
| Maintained by MDSHA, Baltimore DOT, and MDTA | ||||
| Length | 221.31 mi[1][2] (356.16 km) | |||
| Existed | 1926–present | |||
| Tourist routes |  Historic National Road Journey Through Hallowed Ground Byway Chesapeake and Ohio Canal Scenic Byway Antietam Campaign Scenic Byway | |||
| Major junctions | ||||
| West end |  US 40 at Pennsylvania border near Keysers Ridge | |||
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| East end | US 40 at Delaware border in Elkton | |||
| Location | ||||
| Country | United States | |||
| State | Maryland | |||
| Counties | Garrett, Allegany, Washington, Frederick, Carroll, Howard, Baltimore, City of Baltimore, Harford, Cecil | |||
| Highway system | ||||
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U.S. Route 40 (US 40) in the U.S. state of Maryland runs from Garrett County in Western Maryland to Cecil County in the state's northeastern corner. With a total length of 221 miles (356 km), it is the longest numbered highway in Maryland. Almost half of the road overlaps or parallels with Interstate 68 (I-68) or I-70, while the old alignment is generally known as US 40 Alternate, US 40 Scenic, or Maryland Route 144 (MD 144). West of Baltimore, in the Piedmont and Appalachian Mountains / Blue Ridge region of the Western Maryland panhandle of the small state, the portions where it does not overlap an Interstate highway are mostly two-lane roads. The portion northeast of Baltimore going toward Wilmington in northern Delaware and Philadelphia in southeastern Pennsylvania is a four-lane divided highway, known as the Pulaski Highway (named for American Revolutionary War (1775–1783) foreign military volunteer of Polish cavalry officer Casimir Pulaski, 1745–1779). This section crosses the Susquehanna River at the north end of the Chesapeake Bay on the Thomas J. Hatem Memorial Bridge.
From Cumberland on the western branch of the Potomac River and terminus of the historic Chesapeake and Ohio Canal, west to Pennsylvania, US 40 is the successor to the historic route of the National Road, first Federal interstate road built in the early 19th century which eventually ran from Baltimore west, through Ohio, Indiana, and Illinois to Vandalia, then territorial capital of the Illinois Territory near the Mississippi River.
East of Cumberland, towards Baltimore, US 40 follows several former private company turnpikes, most notably the Cumberland Turnpike, Baltimore and Frederick-town Turnpike, later known as Frederick Road (MD 144) between Baltimore and Frederick.
The route from Baltimore northeast to the Delaware state line follows another historic East Coast / Northeast Corridor routing towards Philadelphia, New York City and Boston including the old Baltimore and Havre-de-Grace Turnpike (now mostly bypassed and known as the Old Philadelphia Road, MD 7).