Employees of Lawrence's Kmart distribution center, Ed Robb, of Lawrence, a 40-year employee still working at the plant, left, and Dale Heston, of Oskaloosa, who retired after 35 years with Kmart, visit Tuesday at the plant during a celebration of its 40th anniversary in Lawrence.

There was a time that former Kmart Distribution Center employee Dale Heston had about 15,000 numbers stored in his head — each one representing a different product warehoused in the massive facility north of Interstate 70 in Lawrence.

On Tuesday, however, employees of the distribution center had just one number on their minds: 40. More than 300 Kmart employees and retirees celebrated the 40th anniversary of the distribution center with a special luncheon and program.

“We’re very proud of what we do here and very proud to be in Lawrence,” said Jeff Diamond, general manager of the 1.39 million square foot facility that sits north of the West Lawrence interchange of the Kansas Turnpike.

The distribution center serves about 80 Kmart stores in the central United States, as well as serving as a distribution hub for Kmart’s 10 other distribution centers across the country, Diamond said.

On Tuesday, both former and current employees looked back at how much had changed since the facility first started shipping out products in 1972.

“In the early days, we kept track of everything with paper and cards,” said Duane Curtiss, who retired from Kmart after 35 years with the center. “Every time you touched a pallet, you wrote it down somewhere.”

The lack of computers caused some employees — like Heston, who also retired after 35 years with the company — to simply start memorizing numbers they worked with on a daily basis. These days, though, memorizing 15,000 product codes wouldn’t cover even half of the items in the distribution center. The warehouse currently has about 38,000 different products in stock.

“We’ve got everything from shampoo to trampolines in this place,” Diamond said.

About 50 trucks arrive at the center each day with new merchandise, and about 50 trucks depart each day.

Employees also come and go, but Kmart officials said the center has been a longtime employer to more Lawrence residents than people might expect. Of the approximately 300 employees at the center, about half have 20 years or more of service at the company, said Jill Dugan, human resources manager for the center.

“What I’ve had several employees tell me is that they came here when they were 18 and thought it would just be a job, but they found out it was a pretty good way to provide for their families,” Dugan said.

Heston, who has both a son and a daughter who now work at the center, said he’s hopeful the facility will be a major part of the Lawrence business scene for years to come. Worries were high in 2002 when the entire Kmart Corporation filed for bankruptcy protection. Many retail analysts questioned whether the chain could survive, and its parent company — Sears Holding Corp. — did shutter several stores after slow holiday sales in 2011. But Heston said he’s still betting on a turnaround by the company.

“They have a lot of folks who have worked hard to make it better, and I think they’re on the right track,” Heston said.