Don T. Nakanishi, the director of the Asian American Studies Center at the University of California, Los Angeles, told the Berkeley Web site: “Ron Takaki elevated and popularized the study of America’s multiracial past and present like no other scholar, and in doing so had an indelible impact on a generation of students and researchers across the nation and world.”  Ronald Toshiyuki Takaki was born in Honolulu and, in his youth, spent most of his time surfing. On the beach, he was known as Ten-Toes Takaki for his hang-ten style.  He found his vocation while earning a bachelor’s degree in history at the College of Wooster in Ohio. While in Ohio he married Carol Rankin, who survives him. Besides his son Troy, of Los Angeles, he is also survived by another son, Todd, of El Cerrito, Calif.; a daughter, Dana Takaki of Chester, Conn.; a brother, Michael Young of Thousand Oaks, Calif.; a sister, Janet Wong of Chatsworth, Calif.; and seven grandchildren.  He continued his education at Berkeley, where he earned a master’s degree in 1962 and a doctorate in history in 1967. He was deeply influenced by the Free Speech movement at the university and by the civil rights struggles in the South. “I was born intellectually and politically in Berkeley in the ’60s,” he told The San Francisco Chronicle in 2003.  He wrote a dissertation on slavery in the United States and returned to the subject in his first book, published in 1971, “A Pro-Slavery Crusade: The Agitation to Reopen the African Slave Trade.”  At U.C.L.A., Mr. Takaki taught the university’s first black-history course, created in response to the Watts riots. When a student asked what revolutionary tools he would be teaching, Mr. Takaki said: “We’re going to strengthen our critical thinking and our writing skills. These can be revolutionary tools if we make them so.”  In 1971 he became the first full-time teacher in Berkeley’s new ethnic studies department, where he taught a highly influential survey course that took a comparative approach in describing racism as experienced by different ethnic groups in the United States. In addition to helping establish the graduate program in ethnic studies, he helped put in place the requirement that all undergraduates take a course intended to broaden their understanding of racial and ethnic diversity. He retired in 2003.  His many books include “Iron Cages: Race and Culture in 19th-Century America” (1979), “Strangers From a Different Shore: A History of Asian Americans” (1989), “Democracy and Race: Asian Americans and World War II” (1995) and “Double Victory: A Multicultural History of America in World War II” (2000).  A version of this article appears in print on , on Page A26 of the New York edition with the headline: Ronald Takaki, 70, a Scholar on Ethnicity. Order Reprints| Today's Paper|Subscribe
Mr. Takaki made it his life’s work to rewrite American history to include Asian-Americans and other ethnic groups excluded from traditional accounts.