Known as the Harbor Tunnel Thruway, the highway runs 11.44 miles (18.41 km) between one junction with I-95 in Elkridge and another interchange with I-95 on the east side of Baltimore.

In conjunction with a pair of spurs, unsigned I-895A and I-895B, I-895 provides access to the tunnel from I-97 and Maryland Route 2 (MD 2) in Glen Burnie.

In the early 1950s, the Maryland State Roads Commission (SRC) chose to construct a four-lane tunnel between the Canton and Fairfield neighborhoods of Baltimore and approach highways to connect the tunnel with major highways to Washington, D.C.; Annapolis; Richmond, Virginia; and Philadelphia, Pennsylvania.

In 2024, I-895 was designated a main detour route for through non-hazmat traffic in the wake of the Francis Scott Key Bridge collapse.

I-895 crosses the Patapsco River (the Howard–Baltimore county line) and US 1 (Washington Boulevard), then receives the exit 1 flyover ramps from northbound US 1 and to southbound US 1 before passing under I-195 with no access.

The speed limit drops to 55 mph (89 km/h), then the highway crosses MD 648 (Annapolis Road) and curves northeast across marshland, the main line of the Maryland Transit Administration (MTA)'s Baltimore Light RailLink, and the Patapsco River into Anne Arundel County.

East of the river, I-895 receives flyover ramps from the thruway's southern approach, unsigned I-895B, at exit 6 in Brooklyn Park.

I-895 parallels CSX Transportation's Curtis Bay Branch as the highway passes along the northern edge of the Brooklyn neighborhood.

The highway crosses the Curtis Bay Branch on a steel K-truss bridge ahead of exits 8A and 8B.

[6][5] The highway veers northeast and crosses both Amtrak's Northeast Corridor and CSX Transportation's Philadelphia Subdivision railroad lines before exit 13 with US 40 (Pulaski Highway) and MD 151 (Erdman Avenue); the entrance ramp extends from the US 40–MD 151 partial cloverleaf interchange immediately to the north and west.

[10] Shortly after work began on the Patapsco Tunnel Project on April 7, 1955, several changes were made to the plans for the approach highways.

The northern terminus at US 40 was altered to allow an extension from US 40 to the southern end of the future Northeastern Expressway (now the John F. Kennedy Memorial Highway).

[17] In addition, flyover ramps were constructed at the city limits for I-95 to diverge from the John F. Kennedy Memorial Highway onto its own path through east Baltimore in 1970.

[23] The Canton Viaduct, a 3,400-foot (1,000 m) elevated structure carrying I-895 over a railroad yard, Ponca Street and the ramps connecting I-95 to Keith Avenue, was replaced in the late 2010s and early 2020s.

[24][25] The viaduct, next to the toll plaza for the Fort McHenry Tunnel, was one of the oldest Interstate bridges in Maryland.

Similar to what was done in the late 1980s rehabilitation of the tunnel, one side of the viaduct was closed while the other operated with one lane in each direction.

[3][5] The highway was constructed in 1957 to connect the northern end of the Glen Burnie Bypass with the Harbor Tunnel Thruway.

[34] I-895B is the designation for the 2.67-mile (4.30 km) southern approach to the mainline of Harbor Tunnel Thruway between MD 2 (Governor Ritchie Highway) in Glen Burnie and I-895 in Brooklyn Park.