Born in 1923 as Ruth Miriam Wolkowsky in Key West, Florida. At age six months she moved to Miami and was raised there. While growing up, she was unaware of the pervasive segregation of the time, except when visiting her grandparents in Spring Garden. Across the railroad tracks from there was the neighborhood then called Colored Town, and now called Overtown. This town seemed like a strange other world, in which black people had a servile role, doing laundry for white people.

She began studying piano at age 5, and later studied with Mana-Zucca, who moved from New York to Miami. She graduated from Miami Beach High School in 1941, then studied for two years at the University of Miami, then obtained her bachelor's and master's degrees in music at the University of Michigan in Ann Arbor. While studying with the renowned Pianist Artur Schnabel, she broke more racial taboos by dating a classmate who was a young black man from Jamaica. She returned to the University of Miami again to teach piano.

She later left Miami for Paris, France, in 1949, in order to study composition with Nadia Boulanger, the Teacher of such luminaries as Aaron Copland and Astor Piazzolla. Paris of that time was refreshingly integrated, with integration considered as the norm. She married Arnold Merwin Greenfield there, who was an attorney and friend of her brother's from Miami. He enjoyed painting and cooking and listening to his wife play the piano. Her maid of honor was a black Pianist from Tennessee.

Upon returning to segregated Miami, she wanted to do something about the situation. She founded the Fine Arts Conservatory in 1951 along with Tally Brown. The school moved between black and white neighborhoods, holding classes in such locations as private homes, a Masonic lodge, a YMCA and the most notorious location, a storage room for caskets in an Overtown funeral home, that reeked of formaldehyde. On May 9, 1953, Ruth's student, 15-year-old James "Jimmy" Ford performed at an otherwise all-white recital at Miami Memorial Library thanks to Ruth's having alerted Jack Bell, a Miami Herald columnist who wrote about the issue.

Finally in 1961, the conservatory had raised enough money to buy a building that served as its permanent location until it closed in 1978. This was in Liberty City, a black neighborhood around Miami's 60th Street. The conservatory eventually expanded to six branches throughout Miami. Overtown resident Mary Ford Williams helped found the school, while her son James Ford studied piano at the school.

Ruth Greenfield also continued to teach for 32 years at what is today Miami Dade College, Florida's first integrated college. She founded Miami-Dade Community College's Lunchtime Lively Arts Series in the late 1970s and made all-encompassing (including music, theater, and literature). In the fall of 2011, the college rededicated its Wolfson Campus auditorium in her honor.

In 2013, Director Steve Waxman released a feature documentary, "Instruments of Change" about Greenfield and her history with the Fine Arts Conservatory. The film included Miami personalities Eduardo Padron, Marvis Martin, Garth Reeves, Carrie Meek, Judge Wendell Graham, Judy Drucker and Charles Austin.