Polygon Northwest, a Bellevue based home builder, has been sold to Newport Beach, Calif. based William Lyon Homes for $520 million cash.

Polygon has been actively engaged in Issaquah, including purchasing the eastern part of the old Lakeside development property. Polygon is tentatively planning a development of 260 multi-family homes on the 13-acre tract.

Also, last year, Polygon paid $54 million for the 63-acre tract in the Issaquah Highlands, previously owned by Microsoft. Polygon has built nearly 16,000 homes in the Seattle and Portland areas since 1991.

William Lyon Homes will keep the Polygon brand name and 130 employees. William Lyon Homes also has offices in Colorado and Nevada.

In 2013, Polygon earned $292 million in revenue. It is expected to build 850 to 900 new homes in 2014 and 1,100 to 1,200 in 2015. Polygon sells new homes in 12 communities and expects to grow to 16 new home communities by mid-2015.

According to SEC documents, Polygon CEO Jeff Gow, Polygon executives Gary Young, Chris Eadon, Natalie Schmidt, Paulette Murchison, Andy Whisenant and Eric Evans will leave the company once the sale is finalized.

William Lyon expects the acquisition of Polygon to generate significant returns in 24 to 36 months. It has been a publicly traded company since 2013

Numerous attempts by The Reporter for comment from both Polygon and William Lyon Homes were unanswered.