Mordi Gassner, painter, muralist, designer, and printmaker, was born in New York City on May 27, 1899. A prolific artist who found success in several mediums, he nevertheless fell into obscurity by the end of his life, though a discovery of his art in storage in the early 2000s led to a revival of interest in his work. Gassner came from a propserous family in the fur trade, and was an autodidactic artist, learning about art and sciences at the New York Public Library before attending the Parsons School of Design (then known as the New York School of Applied Art) from 1916 to 1919. He also took courses at the Art Students League, where he would later teach. Building a reputation for himself as a designer, he was hired in the early 1920s by Hollywood executives to design sets on the other side of the country in Los Angeles, working on Mary Pickford and Douglas Fairbanks film The Thief of Baghdad, among others.  

In 1928 and 1930 he was awarded Guggenheim Fellowships to study in Florence, Italy. According to the New Yorker's article on the artist in 2001, "The Italians thought so highly of the young painter that they gave him a studio right above Michelangelo's 'David,' in the Galleria dell'Accademia.'" ("A Mothballed Mural," October 22, 2001) While living in Florence Gassner exectued a mural project titled The Mural Monument to Modern Culture, which included several panels dedicated one each to biology, chemistry, physics, geology, the poet Petrarch, archeology/anthropology, and astronomy. They were later exhibited at the Brooklyn Museum (1932), and after their 2001 recovery, five of the panels were put on permanent display at the Polytechnic Building in Brooklyn, NY.

In the years leading up to the Second World War he was hired by the WPA to design and execute several murals for the United States Postal Service as well as the Long Island Counrthouse. It was also at this time that he created a series of lithographs of animals in the wild, done in a nearly Surreal style, considered among his most recongized works despite their scarcity. During the war, Gassner designed manuals for the Army Signal Corp. 

The second phase of Gassner's career was divided between teaching and designing sets and costumes for the theater. Beginning in the 1950s he was a teacher of art history, painting, and scenic design at the New School of Social Research (now called The New School, merged with Parsons) and the Art Students League, and he continued to teach through the 1960s. His career as a designer continued through the 1970s. He died in Drake's Beach, Virginia, in 1995.

Gassner exhibited at the Whitney, the Corcoran, and the Museum of Modern Art, among others. In 2002 the Susan Teller Gallery held a retrospective of his works titled "Mordi Gassner: Painting, Prints, and Unique Works on Paper, 1924 to 1951".