THE WAR YEARS
1940
November 2 5-December 1: Nelson was a participant in the first National Art Week, Philadelphia. He sold one of his first works entitled Bullfight for $15.

1941
Nelson returned from a three-year residence in New York. His wife later reported that Leonard found New York living too social for his tastes, and too demanding. He always said that Philadelphia was the "perfect place" for an artist.

March: First National Print Annual Exhibition, The Brooklyn Museum, March 19-May 4, included two woodcuts, Dance Tapu and Head of a Dancer.

October: Nelson is nominated to the Board of Governors of The Philadelphia Print Club.

1942
On August 1 Nelson was ordered to report for induction into the Army on August 8. He became a Private in the Medical Detachment at Fort Eustis, Virginia. After a transfer, he was sent to the Red Cross Unit at the hospital where he designed Christmas murals and wall drawings for the Medical Detachment dance.

He contributed to a WPA project, requiring the construction of 100 triangular containers with caricatures of Hitler, Mussolini, and Hirohito, the Emperor of Japan. These containers were erected in Philadelphia to collect scrap, and had invitations written on them inviting the citizenry to "jam" down the figures' throats scrap metal and other valuable materials vital to the war effort.

In October he was invited to submit an entry to the Fortieth Annual Exhibition of Water-colors and Prints at the Pennsylvania Academy of the Fine Arts.
In November he participated in a group show called "Reactions to the War," an exhibition of watercolor, gouache, and drawing at Philip Ragan Associates, Inc., in the Broad Street Station Building.

1943
May 25-June 25: Included in an exhibition of "Paintings by 4 Soldiers" at Philip Ragan Associates with William Erno Mackey, Leonard Nelson, Isaac Newport, and Stewart Wheeler, who later became a well-known Surrealist artist exhibiting regularly in New York and Philadelphia. Nelson left the Army with an Honorable Discharge September 15.

1944
He held the first of 8 one-man shows at the Dubin Gallery, Philadelphia, and entered the Sixteenth Annual Exhibition by Philadelphia Artists at The Print Club, showing a work entitled What Profits a Man?

1945
February: Nineteenth Annual Exhibition of American Wood Engravings, Woodcuts, and Blockprints. An Honorable Mention went to Leonard Nelson for Break the Chains. On November 23 Nelson showed at the Seventeenth Annual Exhibition of Philadelphia Artists at The Print Club.

December: A Christmas Group Show, Selections from $30 to $300, December 3-29, at the Mortimer Brandt Gallery, 15 East 57th Street, NY, where Betty Parsons was the director. Nelson was among the initial group of artists later shown by Parsons when she opened her new gallery in 1946 at 15 East 57th Street in New York.

1946
March: Nelson showed with the Vanguard Group at The Print Club in Philadelphia. It was progressive in viewpoint, and it featured "intaglio, relief, stencil, and chemical printing," as reported in the Christian Science Monitor.

On June 6 Nelson received a Bachelor of Applied Arts Degree in Education from the School of Industrial Art.

November 6-December 15: The Brooklyn Museum, Vanguard Exhibit. This printmakers' group had formed originally in Chicago in June 1945, and it included a number of leading international printmakers, among them Stanley William Hayter who was famous for his downtown New York teaching studio, Atelier 17.

1948
Nelson leaves the Betty Parsons Gallery, and begins to show at the Peridot Gallery in New York the following year. He also begins teaching at The Print Club (1948-1951) and at the Hussian School of Art (1948-1951).

January: Awarded purchase prize for Dance for Midzimue by the jury of the Twenty-second Annual Woodcut and Wood Engraving Exhibit, Print Club.

March 30: "3 Jazz Murals" by Loos, Mackey, and Nelson exhibited at Billy Krechmer's Jam Session Club.

May 16: He shows his Pandora's Box at The Print Club, a device for creating hundreds of compositions by the positioning and movement of large plate glass slide panels covered with theatrical jells, lace, and string.

1948-1949
November 17-April 13: Nelson teaches at the Philadelphia Museum of Art.

1949
March: Nelson's Nickelodeon is featured at a Print Club Workshop exhibit along with prints by students and the Faculty from Moore College of Art.

May 2-May 24: Peridot Gallery Exhibition at 6 East 12th Street, New York. Reviewed in Art Digest, The New Yorker and Art News.