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Al·ta California(äl′tə) also Upper California
The former Spanish possessions along the Pacific coast north of the peninsula of Baja California. Early maps of the area often depicted California as an island. When this misconception was corrected in the 18th century, the peninsula came to be called Baja California and the rest of the mainland, Alta California.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.