Around the time Dillingham was dreaming of his railroad, another businessman, James Campbell successfully dug ʻEwa's first artesian well in 1879, effectively solving the water problem.

Campbell, who had purchased 40,000 acres (16,200 ha) of ʻEwa land thought he might start a cattle ranch, but quickly realized that ʻEwa's rich volcanic soil (which overlays a massive ancient coral reef) combined with year-round sunshine and a supply of water was ideal for growing sugarcane.

While Dillingham's dream of large-scale settlement on the ʻEwa Plain would have to wait until the last decades of the twentieth century, his plan for a railroad to the area came together quickly.

He leased Campbell's ʻEwa and Kahuku land to start two sugarcane plantations and obtained a government railroad charter from King David Kalākaua on September 11, 1888.

After securing the capital, Dillingham broke ground in March 1889 to connect the 12 miles (19 km) between Honolulu and ʻAiea (as demanded in the charter) by fall 1889.

Although progress stalled during the chaos of the late Kingdom and early Republican periods, by 1895 the railroad had passed through what would become the junction of Waipahu, traversed the ʻEwa plain, and was skirting the Waiʻanae coast to a sugar mill there.

After issuing gold bonds in January 1897 the company extended the railroad around Oahu's rugged Kaʻena Point to Haleiwa on the north shore by June 1897, where Dillingham built a hotel.

In 1906 an 11-mile (18 km) branch line was constructed from Waipahu up the Waikakalua Gulch to Wahiawa and the pineapple fields of central Oahu.

For instance, besides sugar and pineapples, the railroad hauled garbage from Honolulu to a dump on the Waiʻanae Coast, sand from Waiʻanae to Honolulu during the development of Waikiki, and served the major military bases: Pearl Harbor, Hickam Field, Barber's Point Naval Air Station, Schofield Barracks, and Wheeler Army Airfield.

The OR&L train station was converted to a Honolulu Rapid Transit bus terminal after 1947 (later discontinued), and added to the National Register of Historic Places in 1979.

On December 31, 1947, a final excursion carrying company President Walter F. Dillingham (Benjamin Dillingham's son), along with numerous guests, departed from Kahuku behind American Locomotive Company steam engine number 70 through 71.4 miles (114.9 km) of countryside back to the Honolulu station.

The Hibiscus & Heliconia Short Line Railroad (H&HSL RR) was formed in 1948 by local rail fans and modelers.

Due to a lack of money and enthusiasm the group was unable to remove their two coaches from the property, so a plantation official had them torched.

The Navy, especially during the Korean War and the Vietnam War, ran ammunition trains between the West Loch of the Pearl Harbor Naval Base, through the ʻEwa Plain, to the Lualualei Naval Ammunition Depot on the Waiʻanae coast, preserving one of the most famous and scenic stretches of the railroad.

In that same year a small group of railroad fans on Oahu learned of the abandonment and petitioned the Navy to turn the line and equipment over to them.

Nicholas Carter, a charter member of the HRS and one of its founders worked with others in the early 1970s, nominating the former OR&L mainline from ʻEwa to Nānākuli to the National Register of Historic Places.