Photos show what Costco looked like when it first opened in 1983

Brotman, who died in 2017, was an attorney who was inspired to open a European-style wholesaler after taking a trip to France.

"I called around to retail contacts and asked them to list executives who could run such a business. Jim was on most lists. I cold-called him one day and flew to California to meet him," Brotman said.

Price was a titan in American retail, and a close mentor to Sinegal.

Located in an old airplane hangar, Price Club exclusively offered memberships to small business owners.

A key difference between the brands: Costco would appeal to non-business members as well.

Company sales in that first year reached $101 million, according to SEC filings.

Non-members could shop as long as they paid a 5% surcharge on their purchases.

"We didn't have many of the enhancements that we've added to the business since then," he said. "It was clearly a warehouse; an open-beam ceiling and cement floors and industrial steel and forklifts moving around in the facility. As time has gone on, the model has incorporated a lot of new things that we've put into the business."

Even now, Costco warehouses only offer about 4,000 SKUs, as compared with about 30,000 at a conventional supermarket, or more than 100,000 at a Walmart store.

Sinegal served as Costco's CEO from 1983 until his retirement in 2011.

"The original business plan called for eventual growth to about 12 Costcos, primarily in the Northwest, and maybe $80 million in sales per store," Sinegal told CNN in 2009.

Costco's second and third locations were in Portland, Oregon, and Spokane, Washington.

Founder Sam Walton specifically credited Price with inspiring some of his best ideas: "I guess I've stolen – I actually prefer the word 'borrowed' – as many ideas from Sol Price as from anybody else in the business," he said.

"That's why we expanded as fast as we did," Brotman said.

"We are working to get established in certain markets, to preempt those markets," he said. "That's why we expanded as fast as we did (12 stores in 18 months and six more scheduled this year), and that's the posture you'll see taken by most of the other companies."

Membership fee revenue totaled $1.3 million in the first year, per SEC filings.

"It's one of the most exciting concepts to come along in many years that is truly different," said Ronald Loveless, the head of Sam's Club, told the news service at the time.

The company held its initial public offering in 1985, selling shares for $10.

The value of one of those initial shares today? A combined total of more than $5,000.

At that point, the chain boasted "17 locations, 1.3 million members, and 3,740 employees," according to Costco's website.

Before the merger, the top three warehouse club chains were mostly regionalized, with Costco in the Northwest, Price Club in the Southwest, and Walmart-owned Sam's Club in the Midwest and Southeast.

The first UK location opened that year, followed by the first Asian location in Seoul in 1995.

"When I was a corporate auditor for the company, the first thing the folks at the warehouse would ask me is, 'Are you red or blue?'" a former employee told Business Insider.

At its 40th anniversary in 2023, Costco had 838 locations around the world, nearly 129 million membership cardholders, $237.7 billion in revenue.