William Wrigley Jr. settled in Chicago in 1891. He was only 29 and wanted to build a company. His father was a scrubbing soap manufacturer. So when he moved to Chicago, he started selling his father's soap.
To incentivize people to buy his soap, he started giving out a can of baking soda along with it. When the baking soda proved to be more popular than the soap, he decided to switch to selling baking soda full time.
History has a funny way of repeating itself. Someone suggested that Wrigley give away a couple of packs of bubble gum with each baking soda purchase. Eventually the bubble gum became so popular, Wrigley switched to bubble gum full time.