Costco and Sam's Club have been duking it out in the wholesale market. Here's how their rivalry began and later intensified.

Ron Vachris is Costco's third CEO in its 40-year history. He started out as a forklift driver while at college.

Jim Sinegal, played a big role in its initial success. After leaving Price Club, Sinegal and Jeff Brotman worked together to co-found Costco Wholesale, which they basically modeled after Price Club.

The company has continued to grow and see sales increase. Costco's founder Jim Sinegal credits the company's unusual business strategy with its success. Sinegal, whose company has been called the ...