Welcome to Diamond Bar, California! The city is named after the "diamond over a bar" branding iron registered in 1918 by ranch owner Frederick E. Lewis and is located at the junction of the Pomona and Orange freeways. Diamond Bar is primarily residential with shopping centers interspersed throughout the city. Diamond Bar is also the location of the well known '' Diamond Bar Center', owned by the city of Diamond Bar. This facility has meeting and banquet rooms, large and small to accommodate the most lavish weddings to business meetings. To find beautiful homes for sale in Diamond Bar, click below.