Amazon has narrowed the list of cities vying to become the future site of Amazon HQ2 from 238 down to 20.

Donald Bren, the richest real estate developer in the US, wrote a letter in October to Jeff Bezos, offering to finance the entire $5 billion project.

Bren hoped to convince Bezos to make Irvine, California the home of HQ2, but it was notably absent from the list of 20 cities still in the running.

The fight for Amazon's HQ2 has turned a corner.

On Thursday, Amazon announced the 20 cities still in the running to become for HQ2 — narrowed down from 238 cities that submitted proposals last year.

Atlanta, Miami, Nashville, and Toronto are among the places that made the cut. Los Angeles is the only city in California on the short list.

Notably absent from the list is Irvine, California, home of the richest real estate developer in the US: Donald Bren. Back in October, the Southern California city took desperate measures to draw Amazon CEO Jeff Bezos' attention.

Donald Bren, the multi-billionaire owner of the Irvine Company, wrote a letter to Bezos on behalf of his company and in companion with the city of Irvine.

In it, he offered to finance the entirety of HQ2 — which Amazon projects will cost about $5 billion — if the e-commerce giant picked Irvine. The offer is billed by Bren as "a one-click shopping opportunity" for Amazon.

Bren writes:

"With the Irvine Company proposal, Amazon will not be required to invest capital for land acquisition, buildings, or entitlements to build your new business campus. Our company has the long-term real estate assets, capital resources, and flexibility to deliver all your required workspace with lease durations of Amazon's choosing.

"In essence, you would have a one-click shopping opportunity and be able to capitalize on our inplace property development rights, thus avoiding potential delays, because Irvine Company has invested more than 60 years master planning 93,000 acres of land, and designing and overseeing the creation of the largest new city in America…Irvine, California."

Over 250,000 people live in Irvine and it's often regarded as the epicenter of Orange County, an affluent coastal community sandwiched between San Diego to the South and Los Angeles to the North.

Amazon says its new HQ2 will eventually house 50,000 mostly white-collar workers making an average of over $100,000 a year. That's currently about the average income for workers in Irvine.

Bren — who's worth a cool $17 billion — is the chairman of the Irvine Co., which owns about one-fifth of the land in Orange County spread across office, retail, and apartment space, as well as golf courses and hotel resorts.

In the letter, Bren positions Irvine as the ideal candidate for Amazon because "Irvine is ranked by various sources as America's fastest growing, most desirable, best educated, safest, and healthiest large city," he writes.

More than 900 tech companies, such as Google, Broadcom, Blizzard Entertainment, UBS, and Verizon have offices in Irvine, and Amazon already has a 1,200-person outpost in the city.

Southern California is home to the biggest pool of STEM workers in the US, according to the Irvine Company proposal. The University of California, Irvine, a top-ranked public university located in Orange County, awards 42% of its undergraduate students with STEM degrees annually.

At the end of the letter, Bren makes one final plea to his fellow billionaire: "It's 74 degrees on this beautiful October day, the sun is out and the surf's up at our spectacular beaches. Please come join us! The water, like the place, is the perfect temperature."

Weather — and financial support — were seemingly not enough to draw Bezos' interest. Perhaps not surprising, given the richest man in the world calls Seattle home.

Read Donald Bren's letter to Jeff Bezos in full below: