John William Casilear started his career as an engraver. He worked under engraver Peter Maverick. Most of his early work was in the creation of bank notes but he soon put his efforts toward creating engravings of the noteworthy paintings of contemporary artists.
After submitting some of his engravings to the National Academy of design in the early 1830's, he was admitted to the Academy in 1833. His paintings were shown at the Academy over subsequent years and, in 1851, he was given the title of an Academician.
His work is considered to be of the Hudson River School and he is one of the more noteworthy artists of that style. His paintings were very successful in his time and by 1854, after studying the work of the Old Masters who he so admired in Europe with several other painters, he was presiding over his own studio in New York City. Upon opening his own studio, he was able to give up his engraving and to become a full time landscapist.
John William Casilear travelled widely throughout his life, sketching the locations to which he travelled and developing and refining his style. His active career spanned into the early 1890's.