Atwood is a small neighborhood in Placentia, California. It was named for W. J. Atwood, an oil company executive, and was formerly an unincorporated town within Orange County. Its unofficial boundaries are defined roughly as the area of Placentia in the square formed by Orangethorpe Ave., Van Buren St., Lakeview Rd. and Miraloma Ave. There is a post office in Atwood with a ZIP code of 92811. However, this ZIP code is only used for PO boxes. All non-PO box addresses in Atwood are listed as "Placentia" by the United States Postal Service (with the exception of the post office itself: 1679 E. Orangethorpe Ave. Atwood, CA 92811). In 1938, floodwaters inundated a good part of Atwood, where 43 of the 50 deaths in Orange County occurred because of this flood. This catastrophe led to the construction from 1938 to 1941 of the Prado Dam upstream near Corona.
There is a small business area of the community along Orangethorpe Ave. that includes the post office and restaurants, markets, a bar and other stores that cater to the area's predominant Hispanic population. The Parque de Los Ninos city park can be found in the area along with a portion of a busy line of the BNSF Railway that runs parallel to Orangethorpe Ave. In April 2002, that line was the site of a crash between a Metrolink commuter train and a freight train.