The 4.1-mile-long (6.6 km) loop route connects exits 13 and 19 on H-1, passing Fort Shafter, Tripler Army Medical Center, and the Red Hill Underground Fuel Storage Facility.

H-201 serves as an alternate route to H-1 near Downtown Honolulu, traveling on the Moanalua Freeway around the northeast side of Salt Lake.

The freeway continues southeast, passing Moanalua Gardens and an industrial area, before it bisects Fort Shafter, a military installation in the Kalihi valley.

[10][11] The territorial government began preliminary construction of a four-lane divided highway to replace Moanalua Road in 1948, following the opening of the new Tripler Army Hospital.

[12][13] The project, which would reduce the number of curves on the road from 24 to 6, was also meant to connect with the Mauka Arterial (now part of H-1) and relieve congestion on the Kamehameha Highway near Pearl Harbor.

[17] The remaining section of the original Moanalua Road, bisecting Fort Shafter, was upgraded to a divided highway in the second phase and end at an interchange with the Lunalilo Freeway (also part of H-1).

[37] HDOT requested that the Moanalua Freeway be reclassified as an Interstate so that the interchange with H-1 at the eastern end could conform to federal highway standards.

Reasons given included the following: In July 2004, in conjunction with a major resurfacing of both sides of the freeway, it was decided to bring the signage in line with the official designation.