They began singing together as children at their mother's Ohio church and then performed at weddings and church revivals. They got their big break on Arthur Godfrey's Talent Scouts show in 1952 where they continued to perform for seven years.
The group made numerous appearances on television and toured into the late 1960s, making a last performance together on The Ed Sullivan Show in 1968. Dorothy stepped back to raise her two sons, Williamson said. Christine also raised a family while Phyllis pursued a solo career, according to a 1986 profile in People Magazine after the trio reunited and began doing nightclub and Las Vegas performances again.
The sister last performed together in the mid-2000s, and are featured on a 2004 PBS show called "Magic Moments - Best of 50s Pop."
"They were a talent at a time when you had to have talent - it couldn't be done as it is now," said Williamson, who is married to McGuire's son, Rex. "Truly, their harmonies were some of the best and God-given and they always knew that and never took that for granted."
The group performed for five presidents and Queen Elizabeth II of Great Britain. They were inducted into the National Broadcasting Hall of Fame in 1994 and the Vocal Group Hall of Fame in 2001.
Christine and Phyllis, 86 and 81 respectively, live in Las Vegas.
"They were just hard working professionals and they took every aspect of the career very, very seriously," Williamson said of the sisters. "And when they put on a show you were going to get a great, great show."
McGuire was married for 53 years to Lowell Williamson, a wealthy oilman. The couple had two sons, Rex and David.
In addition to her husband and sons, she is survived by two step-children and nine grandchildren.
A memorial service is set for Sept. 15 at Valley Presbyterian Church in Paradise Valley.