He became a staff artist of the Philadelphia North American newspaper, for which he produced features like the comics strip Toyland, illustrations for the serialization of 'The Fate of a Crown' (a book by L. Frank Baum), Children's Stories That Never Grow Old, and the Sunday comics page 'The Little Journeys of Nip and Tuck' with verses by W.R. Bradford (1909–1910).

However, as the series expanded, Neill brought his own unique flair to the illustrations, showing more artistic representations of the characters as well as beautiful paintings of numerous scenes.

Neill's illustrations were published in the leading magazines of the first few decades of the twentieth century, including Collier's, Vanity Fair, The Saturday Evening Post, The Ladies Home Journal, Century, Pictorial Review, The Delineator, Boys' Life, St. Nicholas, The People's Home Journal, Adventure [3] and many others.

Dorothy drawn by Denslow appeared to be a chubby five- or six-year-old with long brown hair in two thick braids that remained untied at the ends.

His last work, The Runaway in Oz, was drafted before his death, but the full illustrations were never finished and Reilly & Lee decided not to publish the manuscript.

However, Neill's widow kept the manuscript safe, and, in 1995, it was finally published by Books of Wonder and edited and illustrated by Eric Shanower.