<Tr> <Th> Children </Th> <Td> </Td> </Tr> <Tr> <Th> Parent (s) </Th> <Td> Charles MacArthur Helen Hayes </Td> </Tr> <P> James Gordon MacArthur (December 8, 1937--October 28, 2010) was an American actor best known for the role of Danny "Danno" Williams, the reliable second - in - command of the fictional Hawaiian State Police squad in the long - running television series Hawaii Five - O . </P> <P> Born in Los Angeles, MacArthur was the adopted son of playwright Charles MacArthur, and his wife, actress Helen Hayes . He grew up in Nyack, New York, along with the MacArthurs' biological daughter, Mary . He was educated at Allen - Stevenson School in New York, and later at the Solebury School in New Hope, Pennsylvania, where he starred in basketball, football and baseball . In his final year at Solebury, MacArthur played guard on the football team; captained the basketball team; was president of his class, the student government, and the Drama Club; rewrote the school's constitution; edited the school paper, The Scribe; and played Scrooge in a local presentation of A Christmas Carol . He also started dating a fellow student, future actress Joyce Bulifant; they were married in November 1958 and divorced nine years later . </P>

Who played dano on the original hawaii five-0