Mary Lee started singing at a very young age of six and often practised with her older sister, who already had experience in performing at several events in the LaSalle County situated in Illinois. The three sisters often performed together at various events, but it was in the year 1938 when Mary Lee was spotted and selected by the Ted Weems Orchestra. She often travelled with her sister Vera Mae and mother while on four months outing with the Ted Weems Orchestra group. She considered her mother and older sister as her biggest mentor. While working with the Ted Weems Orchestra, she recorded many songs which include a duet with Elmo Tanner in the year 1939 named Back To Smokey Mountain. She then went on to record eight songs in the year 1942 with the Bob Crosby’s Bob Cats. In the year 1998, a compilation of songs of Mary Lee from Gene Autry films was released which included tracks like Sing a Song of Laughter from the 1941 film Riding on a Rainbow and Give Out with a Song from the 1940 film Gaucho Serenade.

On February 18, 1939, Mary Lee made her debut in acting by portraying the role of Mary Nickerson in Nancy Drew...Reporter, a Warner Bros movie. She was also made to sing for a Nursery Rhyme Medley. She joined Republic Pictures in 1939 and was seen in the movie South of the Border On December 15, 1939. In the year 1940, she went on to sign a five-year contract with the Republic Pictures and acted in nice Autry films. She portrayed the role of Patsy, the female protagonist’s younger sister in most of these films. The Singing Hill released on April 26, 1941, was her last Autry film. She further worked on nine Republic feature movies. In the year 1943, Mary Lee went on to do several B musicals which include Shantytown released on April 20, 1943; Three Little Sisters released on July 31, 1944, and Nobody’s Darling released on August 27, 1943. Song of Nevada released on August 5 in the year 1944 was her last film and after which she was not seen in movies at all.

She married Harry J. Banan on November 12, 1943. Mary Lee’s husband Harry was a First Sergeant in the United States Army and died in the year 1990. They were proud parents of two children, Harry Philip and Laura Lee. On June 6, 1996, at the age of 71, Mary died in Sacramento situated in California. According to her biography, a very little is known about her net worth.