The following highways are numbered 42.
National Route 42 – part of Cunningham Highway 
County Road 42 (Essex County, Ontario) 
Ontario Highway 42)
Simcoe County Road 42 
Thailand Route 42 (Sadao-Sungai Kolok)
Interstate 42 (proposed)
U.S. Route 42 
Alabama State Route 42 (former)
Arkansas Highway 42 
California State Route 42 (former) 
Colorado State Highway 42 
Connecticut Route 42 
Delaware Route 42 
Florida State Road 42 (former) 
Georgia State Route 42 
Georgia State Route 42A (former)
Illinois Route 42 (former) 
Illinois Route 42A (former)
Indiana State Road 42 Iowa Highway 42 (former)
K-42 (Kansas highway) 
Louisiana Highway 42 
Louisiana State Route 42 (former)
Maryland Route 42 
M-42 (Michigan highway) 
Minnesota State Highway 42 
Mississippi Highway 42 
Missouri Route 42 
Montana Highway 42 
Nebraska Highway 42 (former) 
Nevada State Route 42 (former) New Jersey Route 42 
New Mexico State Road 42 
New York State Route 42 
County Route 42 (Allegany County, New York) County Route 42 (Cattaraugus County, New York) County Route 42 (Chautauqua County, New York) County Route 42 (Chenango County, New York) 
County Route 42 (Dutchess County, New York) 
County Route 42 (Erie County, New York) County Route 42 (Genesee County, New York) County Route 42 (Herkimer County, New York) 
County Route 42 (Livingston County, New York) County Route 42 (Madison County, New York) 
County Route 42 (Putnam County, New York) 
County Route 42 (Rensselaer County, New York) 
County Route 42 (Rockland County, New York) County Route 42 (Schoharie County, New York) County Route 42 (St. Lawrence County, New York) 
County Route 42 (Suffolk County, New York) County Route 42 (Ulster County, New York) 
County Route 42 (Warren County, New York) 
County Route 42 (Washington County, New York) County Route 42 (Wyoming County, New York) 
North Carolina Highway 42 
North Dakota Highway 42 
Ohio State Route 42 (1923-1927) (former)
Oklahoma State Highway 42 
Oregon Route 42 
Pennsylvania Route 42 
South Carolina Highway 42 (1920s) (former)
South Dakota Highway 42 
Tennessee State Route 42 (former)
Texas State Highway 42 
Utah State Route 42 
Virginia State Route 42 
West Virginia Route 42 
Wisconsin Highway 42 | Preceded by 41 | Lists of highways 42 | Succeeded by 43 |
