Skip to main content
Completion Date
Project Type
Honolulu, HI
21 18 34.6 N
157 51 46.4 W


The Kamehameha V Post Office building is the oldest public building in the United States to incorporate structural elements of reinforced Portland cement concrete.

"Built of the best materials and in the most faithful manner, it is calculated to stand for an indefinite period proof against the gnawing tooth of time or the ways of the elements."
- Editor, Pacific Commercial Advertiser March 25, 1871

The Kamehameha V Post Office is the oldest surviving public building in the U.S. constructed with reinforced concrete. The success of this early structure helped establish the value of reinforced concrete as a durable construction material.

Brickmaker J.G. Osborne was chosen to provide design and construction. He immigrated to Hawaii from Yorkshire, England, and was aware of the recent development of Portland cement and its expanding use in Europe. It is believed that the leaders of Hawaii were anxious to adopt British skills, which influenced their selection of Osborne.

Because of Honolulu's warm climate, the concrete was carefully wetted and left to harden slowly. While this meticulous curing effort delayed the construction schedule, the city's Superintendent of Public Works believed the care was essential for such a novel idea as a concrete building.