MacKnight's work falls under the post-Impressionism, an art movement that succeeded the nineteenth-century impressionism.
His colorful works were appreciated by amateurs in Boston, who were receptive to impressionist aesthetics.
He painted mostly landscapes and was considered as the equal of John Singer Sargent.
[2] MacKnight became a friend of van Gogh, and introduced him to the Belgian painter Eugène Boch.
The largest collections of MacKnight's works are at the Isabella Stewart Gardner Museum, Boston.