The company originally produced business and advertising films. By 1931 it had moved its principal office to New York City.
In 1937, Castle branched out into 8 mm and 16 mm home movies, buying newsreel footage and old theatrical films for home use. Castle's first home movie was a newsreel of the Hindenburg explosion. That same year, Castle launched his "News Parade" series, a year-in-review newsreel; travelogues followed in 1938. Castle also released sports films, animal adventures, and "old time" movies. The films were sold at camera shops, in department stores, and by mail-order catalog. Castle Films were extensively advertised in national magazines.
Castle obtained home-movie rights to cartoons from several animation studios, including Terrytoons (1938), Ub Iwerks (1941), and Walter Lantz Productions (1947). During World War II it produced numerous documentary and training films for the U.S. armed services. In the late 1940s and early 1950s, Castle released a series of 16 mm "Music Albums" assembled from the Soundies musical shorts, combining three 3-minute songs into each nine-minute subject.
Castle Films distributed two dozen Christmas subjects over two decades, the first being Christmas-Time in Toyland (released in 1939) and the last The First Christmas (in 1959). The perennial in this category was The Night Before Christmas, a live-action dramatization of the poem; this 1946 release remained in print for 26 years.
In 1947, United World Films, Inc., the non-theatrical division of Universal Pictures, purchased a majority stake in Castle Films. Castle subsequently became a Universal subsidiary, drawing upon the studio's library of vintage films (with Abbott and Costello, W. C. Fields, Boris Karloff, James Stewart, etc.). The merger with Universal also brought to Castle the Walter Lantz cartoons with Woody Woodpecker, Andy Panda, Oswald Rabbit, and Chilly Willy. In the 1950s, Castle released a highly successful series of Hopalong Cassidy excerpts, licensed from the series' star William Boyd. When Universal was purchased by MCA Inc. in 1962, Castle also gained access to the pre-1950 Paramount Pictures sound feature films owned by MCA's TV division, releasing sequences from Cecil B. DeMille's spectaculars and Marx Brothers comedies, among other Paramount titles. Newsreels edited from NASA footage of U.S. space flights were timely in the 1960s. Castle's most popular series was its line of science-fiction and horror films, many featuring the Universal Classic Monsters Dracula, Frankenstein, The Wolf Man, The Mummy, The Creature from the Black Lagoon, and The Invisible Man. The series launched in 1957 and grew to 30 titles.
Castle Films changed its name to Universal 8 in 1977 and experimented with longer-length films, but the era of home video brought an end to Universal's home-movie enterprise in 1984. Universal 8 dealt mostly in excerpts, but Universal Pictures Home Entertainment (founded in 1980) offered feature films in their entirety on videotape. Collectors abandoned the excerpts in favor of the complete movies.
The largest U.S. competitor of Castle Films was Official Films, until rival movie studios entered the marketplace, including Columbia Pictures, Warner Brothers and United Artists (under the Ken Films brand name), and 20th Century-Fox.
- Thomas M. Pryor, "Newsreels for the Home", The New York Times, July 4, 1937, p. 100
- Theodore Strauss, "Of One Man's Castle", The New York Times, April 4, 1943, p. X3.
- "United World, Inc., Buys Castle Films", The New York Times, January 2, 1947, p. 22. Eugene Castle became vice president of United World, but resigned in 1949. "Business Notes", The New York Times, December 13, 1949, p. 55.