Leonard Nelson was born Leonard Louis Nelson in Camden, New Jersey on March 5, 1912. Orphaned at the age of 16, Nelson, along with his two sisters lived on trust funds until the stock-market crash of 1929 left them destitute.
In the autumn of 1936, Nelson won a scholarship to the Pennsylvania Academy of the Fine Arts in Philadelphia, though he lacked both a portfolio and a formal art education. He was in fact the Cresson Traveling Fellowship.
After six weeks of touring both Eastern and Western Europe, Nelson returned to Philadelphia and the Academy, earning his certificate in 1939. He took classes at the Barnes Foundation in Merion, Pennsylvania from 1939 to 1941 and became friend with Dr. Barnes and Bertrand Russell, the British philosopher and mathematician.
Drafted into the Army in 1942, Nelson became a Private in the Medical Detachment at Fort Eustis, Virginia. During that time, he designed murals and humorous drawings for the hospital to which he was assigned, as well as for the Works Progress Administration.
After his Honorable Discharge from the Army on September 15, 1943, Nelson focused all his attention on his art, holding shows and participating in exhibitions in Philadelphia and New York City. During that time, he was influenced by Native American art and the Native American-inspired murals of Rufino Tamayo and Diego Rivera.
By the mid 1940s, strong relationships with dealers Peggy Guggenheim and Betty Parsons helped Nelson prosper in the fledgeling New York School. He began to exhibit in the New York galleries, in particular Parsons' gallery. His work reflected the Abstract Expressionist style made famous by this school. Jackson Pollock, Lee Krasner, Willem de Kooning, Adolph Gottlieb, and many others from the New York School were among his contemporaries.
By the late 1940s and early 1950s, Nelson was changing direction. He began taught art at the Moore College of Art in Philadelphia, and began painting in a style that was all his own; a combination of gestural Abstract Expressionism, Color Field, and landscape art. The New York art world disavowed it, nevertheless, it went onto become his signature style.
Feeling hampered by the constraints of the New York School, Nelson relocated to Philadelphia, where he would reside for the remainder of his life. Nelson was aware that relocating could render him obsolete, yet he was willing to take the chance in order to explore his new style.
Nelson spent the 1950s and 1960s teaching at Moore, traveling, painting, and exhibiting. The landscape color field painting style he perfected during that time is the earliest representation of the Philadelphia School of Art. His aesthetic began to influence Philadelphia painters such as Warren Rohrer, Murray Dessner, and Stephen Estock, all of whom incorporated Nelson's tonal, atmospheric, and perceptual qualities suggesting landscape.
Moore College of Art and select Philadelphia galleries regularly exhibited Nelson, with Moore hosting his retrospective in 1977. In 1985 he and his wife of two years Alma, a former Moore student herself, .moved to their permanent home in Berwyn, Pennsylvania.
Sam Hunter described Nelson's 1970s and 80s work as "pathbreaking." Hunter believed that Nelson's name should live among those of color field artists Noland, Olitski, and Frankenthaler, and he ranked Nelson as one of Philadelphia's most important painters.
Leonard Nelson died on November 23, 1993. He was posthumously recognized for originating the Philadelphia School of Art.