A milestone for American renewable energy that has been almost a decade in the making is nearing completion off the coast of Rhode Island. The nation’s first offshore wind farm is now rising and is expected to be completed this fall. Look at the photos above to see details of its impressive construction.

The five-turbine, 30-megawatt project off the coast of Block Island is actually tiny compared to the 100-plus turbine farms that are common in Europe. What will be the world’s largest offshore wind farm, with 300 turbines and 1,800 megawatts, was just approved this week in the U.K. But America has been far slower to adopt offshore wind technology, with proposals stalled by regulators and lawsuits.

Deepwater Wind began construction on the Block Island Wind Farm in 2015. American companies, some from the oil and gas sector, built the foundations and laid undersea fiber cables. GE Renewable Energy is responsible for the turbines themselves, bringing the towers and blades from Europe, where they are made and assembled at a site in Providence over nine months. Each 650-foot-tall turbine has three blades, each weighing 29 tons each and longer than half a football field. The tower itself, broken into three sections, weighs 440 tons.

GE is out on ships now installing the wind turbine structures in a round-the-clock operation that they expect to last a total of about 25 days.

“The tricky part is the weather conditions,” says Eric Crucerey, GE Renewable Energy’s project manager, speaking by phone from aboard the 433-foot-long installation vessel at the Block Island Offshore Wind Farm site. The ship is jacked up to a stable platform and then uses cranes capable of lifting up to 800 tons. Too much wind, and they have to delay the work.

Offshore projects are much more expensive to build than onshore, but because it’s windier off the coast, the projects can ultimately generate more energy once they are built. The Block Island Wind Farm, at a cost of $290 million, is expected to power about 17,000 homes and produce most of Block Island’s energy needs (the island, isolated from the mainland, currently relies on diesel fuel.) But the project created plenty of controversy, both because opponents say they will pay too much for its electricity and from coastal residents who say the turbines will spoil their view.

Some hope the Block Island project opens the floodgates for more offshore wind. Massachusetts just passed a bill requiring utilities to source 1,600 megawatts of offshore wind electricity in the coming decades, and a number of projects are in planning stages up and down the East Coast. One is Deepwater Wind’s 256-square-mile Deepwater One site, which could eventually hold up to 250 turbines. Overall, the U.S. Department of Energy estimates the technical potential for offshore wind in the U.S. to be more than 4,000 gigawatts, much more electricity than the entire country currently consumes.