HILLSBORO, Ore. (KOIN) — Population estimates show tens of thousands of people are expected to move to Washington County over the next few decades, the bulk of whom will settle in Hillsboro, Oregon’s largest city.

The city broke ground August 9 on what will eventually become home to about 20,000 of those new residents.

The South Hillsboro Neighborhood is being developed on 1,400 acres between SW 229th Ave. and SW 209th Ave.

The project has been in the works for more than 20 years and unites 3 land owners to become the largest residential project in Oregon history.

Hillsboro Mayor Jerry Willey, who took office 8 years ago while the project was already well underway, toasted the groundbreaking Tuesday morning.

“Thousands of hours and millions of dollars on just the planning of this to make sure it’s a sustainable and green community,” Willey said.

Joe Hanauer, president of one of the landowning companies, called the cities patience awe inspiring, because by waiting to develop, South Hillsboro can now build a more complete community with multiple parks and housing in all price ranges.

The city’s plan also includes shopping centers and multi-use trails along with schools and transit services.

“It’s sort of 2 plus 2 equals 6 or 8 or 10,” Hanauer said. “If this were done in small pieces, you wouldn’t have that. You’d have everyone looking for the low hanging fruit.”

The Hillsboro School District will be able to build 3 elementary schools, a middle school and a high school on the land.

“We really do feel like we have an opportunity here to be embedded in the community in a very comprehensive way,” HSD superintendent Mike Scott said.

The city hopes to start building houses on the property late next year for the first residents to move in by 2018.