Julius Herman Cosack (February 15, 1826 - May 2, 1892) was a German-American engraver based in Buffalo, New York, in the second half of the 19th century. Cosack was born in Danzig, Germany, where he apprenticed as a lithographic engraver, before emigrating to the United States in 1853. He spent 3 yeas in New York before relocated to Buffalo, where he took work with the lithographic firm of Sage and Sons. There he met the English-American artist and lithographer Hugh De Musgrove Clay (1834 - 1904), with whom in 1864, he founded the lithography firm of 'Clay and Cosack.' The partnership lasted about 13 years before Clay split of, founding another firm with Henry A. Richmond. From 1878 Cosack operated independently as 'Cosack and Company' before taking on Edwin Alonso Clark (1848 - 1881) as a partner in 1880. The firm subsequently operated as 'Cosack and Clark'. Clark died suddenly in 1881, and the firm reverted again to 'Cosack and Company'. Cosack eventually took on Herman T. Koerner (1855 - 1927) and Charles Eugene Hayes (1858 - c. 1910) as partners, but did not change the imprint. The firm became prominent, acquiring a large five store building in downtown Buffalo and installing presses capable of printing 200,000 sheets a day. When Cosack died in 1892, the firm was taken over fully by Koerner and Hayes, who introduced their own imprint.