Why did they call diamond bar diamond bar?

Answer 1

Diamond Bar was the name of a local Ranch that was most of the land that the city is on..

Most ranches got their name in the old west based on the brand they used to mark their cattle. Simple geometric shapes were used as that was the easiest to make into iron and then branded ( burned ) into the cattle of the ranch.

So given that Diamond Bar ranch's symbol was a diamond shape and a line bar, You can see some around the city today

Answer 2

Diamond Bar was named after the "diamond over a bar" branding iron used by ranch owner Frederick E. Lewis in the 1850s. The iron had a diamond-shaped brand over a horizontal bar shape, leading to the naming of the area as Diamond Bar.