Jennewein's father, Emilia Weber Jennewein, was a medalist and die engraver and taught his son the basics of engraving. The younger man then studied drawing, painting, and sculpting at the Stuttgart Museum, where he also worked as an apprentice, and art history and architectural drawing at the University of Stuttgart. He immigrated to the United States in 1907 with hopes of pursuing an art career. While he continued his studies at the Art Students League, he was apprenticed to Buhler and Lauter, a New York firm which specialized in architectural ornamentation. He studied drawing with Geroge Bridgman and painting with Clinton Peters and, in 1911, was commissioned to paint the murals for the vestibule of Cass Gilbert's Woolworth Building in New York. In sculpture, he created four alabaster roundels for Archer Huntington's Fifth Avenue mansion (now the National Academy of Design). In 1912, he was awarded the Avery Prize by the Architectural League of New York and, that same year, began a three-year tour of Europe, visiting France, Germany, Italy, and Egypt.
In 1916, Jennewein won the American Academy's Prix de Rome and studied and worked in the Italian capital from that year until 1920, taking time out in 1918 and 1919 to serve with the American Red Cross during World War I. While in Europe, he modeled a number of mythological and allegorial figures such as Repose, Cupid and Gazelle, Hercules, and Comedy (the last of these was presented to the National Academy as Jennewein's diploma piece in 1933 but it is now unlocated) and married the painter and linguist Gina Pirra.
Jennewein returned to America in 1920 and opened a studio in New York. He worked for a time with the painter Ezra Winter, creating decorations for the Cunard Building in New York, and received an important commission for the Darlington Memorial Fountain for Judiciary Square in Washington, D. C. (The fountain figure, Nymph and Dawn, was replicated for Brookgreen Garden, Murrel's Inlet, South Carolina, in 1940). In 1921, he created the Soldier's and Sailor's Monument for Barre, Vermont, and received the first of several major commissions from the Philadelphia Museum, the most famous being his polychromed ceramic sculptures based on Greek mythology which were placed in the pediment of the west wing of the institution's main building in 1932.
Jennewein was granted another visiting fellowship at the American Academy in Rome in 1924 and took the opportunity to travel through Greece where he researched his figures for the Philadelphia Museum's pediment. Back in America, he worked on sculptures for the Arlington Memorial Bridge in Washington, executed a war memorial for Providence, Rhode Island, and designed the Tours War Memorial for Tours, France, all of this during the late 1920s.
Among his other architectural sculptures are figures for the front of the British Empire Building at Rockefeller Center, New York (begun 1932), and figures for the Department of Justice Bulding, Washington, D. C., dating from the early 1930s. In 1953, he was asked to design a memorial for the American cemetery in Ardennes, Begium, by the American Battle Monuments Commission, and, the following year, he made two reliefs, Orpheus and Ceres, for the doors to central hall of the White House.
For much of his life, the productive Jennewein took an active role in the art world. He began exhibiting at the National Academy in 1924 and taught drawing in the Academy school in the early 1930s. He won the Academy's Saltus Medal in 1942 for The Secret; the Watrous Gold Medal in 1960 for Reflection; the Daniel Chester French Medal in 1972 for Detail "Sancho Panza"; and the 150th Anniversary Gold Medal in 1975 for The Conqueror. He served as viceÄpresident of the Academy (1942-45), president of the National Sculpture Society (1960Ä63), and president of Brookgreen Gardens (1963Ä76). He spent his final years living in Larchmont, New York, while keeping a studio in the Bronx.
