Officials Tuesday marked the completion of two 515-foot tall support towers for the new Gerald Desmond Bridge, a significant milestone after four years of construction and planning for the project.

The towers, which took three years to construct, are now the tallest structures in the city of Long Beach. California’s first cable-stayed bridge, a nearly $1.5 billion undertaking, is scheduled to be complete in 2019.

The new bridge will benefit the entire region, improving traffic flow for truckers and residents, Lou Anne Bynum, president of the Long Beach Harbor Commission, said in a written statement. Roughly 40 percent of the nation’s imports come through the Port of Long Beach and Port of Los Angeles complexes.

Officials will now move to designing the main span of the bridge, which will replace the 50-year-old Gerald Desmond. Construction on that segment is expected to begin in April.

The new bridge is touted by city officials and developers as a project that will redefine the Long Beach skyline, with two massive towers where cables will string out like a fan alongside the six-lane, 1.5 mile roadway. The towers alone will utilize roughly 3,000 tons of rebar and 23,700 tons of concrete.

The bridge, however, is roughly a year behind schedule and $500 million over budget, which officials have blamed on the arduous process of relocating utility lines, capping old oil wells and demolishing structures. Issues with the soil make-up have also caused problems, particularly in the design of the support towers, which have a pile depth of 180 feet below ground.

Harbor officials broke ground on the project in January 2013. It is funded by a combination of port and state funds, and will be managed by Caltrans when complete.