In 1905, Richard Hellmann opened a delicatessen in New York City, where he used his wife’s recipe to sell the first ready-made mayonnaise. It became so popular that he began selling it in bulk to other stores. In 1912 he built a factory for producing Mrs. Hellmann’s mayonnaise in jars. It was mass marketed and called Hellmann’s Blue Ribbon Mayonnaise.

While Hellmann’s Mayonnaise thrived on the East Coast, the California company Best Foods introduced their own mayonnaise. Best Foods Mayonnaise became popular on the West Coast.

In 1932, Best Foods bought out the Hellmann’s brand. By then both mayonnaises had such commanding market shares in their respective halves of the country that the company decided that both brands and recipes be preserved. To this day:

Best Foods Mayonnaise is only sold west of the Rocky Mountains, specifically, in or west of Montana, Wyoming, Colorado, and New Mexico.
Hellmann’s is sold east of the Rockies, specifically, in or east of North Dakota, South Dakota, Nebraska, Kansas, Oklahoma, and Texas.[1]
In 1955, Best Foods acquired Rosefield Packing Co., makers of Skippy peanut butter. Then Best Foods was bought by Corn Products Refining Company in 1958 to form Corn Products Company, which in 1969 became CPC International Inc.

In 1995, Bestfoods split from CPC International, becoming its own company once more. The company was acquired by Unilever in 2000.

In the United Kingdom, Hellmann’s mayonnaise arrived in 1961. Unilever says that it had over 50% market share by the late 1980s. [1]