From 1950 to 1952, McWilliams primarily drew
romance comics and
crime comics for
Lev Gleason Publications. From 1961 to 1968, he drew the sea-adventure strip
Davy Jones, a spinoff of
Sam Leff's
Curley Kayoe. McWilliams and writer John Saunders'
Dateline: Danger!, which ran from 1968 to 1974, introduced the first
African-American lead character of a comic strip, Danny Raven, co-star of this adventure series about two intelligence agents working undercover as reporters. Other comic-strip work includes the
Star Trek and
Buck Rogers strips. He worked as an assistant on
John Prentice's
Rip Kirby in 1964 and 1965; on
Don Sherwood's U.S. Marine strip
Dan Flagg from 1965 to 1967; and on
Leonard Starr's
On Stage in 1969 and 1970, and
Al Williamson's
Secret Agent Corrigan in 1975. McWilliams also illustrated for advertising. He drew no confirmed comic-book stories from 1952 through 1965, when he illustrated two tales in
Warren Publishing's black-and-white
horror comics magazine
Creepy. He went on to draw stories in the supernatural/mystery anthology comics
Boris Karloff Tales of Mystery and
The Twilight Zone, two TV-series spinoffs published by
Western Publishing's
Gold Key Comics, along with a smattering of other stories for that imprint — including some issues of the
superhero series
Doctor Solar, Man of the Atom — as well as for Warren and
Tower Comics. McWilliams illustrated the first
graphic novel version of
Dracula, based very closely on
Bram Stoker's book, for
Russ Jones Productions. It was published initially as an
Ace Books paperback in 1966, and most recently has had a deluxe larger-size reprinting as a
Vanguard Productions hardcover in 2021. Concentrating on
Dateline: Danger!, he drew no comic books from 1968 to 1974. That year he did three supernatural stories for
Red Circle Sorcery and
Mad House, from
Archie Comics'
Red Circle Comics imprint, along with a handful of stories for
Atlas/Seaboard Comics. He
inked roughly a half-dozen
Marvel Comics stories in 1975 and illustrated the first issue of DC Comics's
Justice Inc. before returning to Gold Key, where he drew and
lettered stories through 1982. His work there included issues of
Flash Gordon and the TV-spinoff comic
Buck Rogers in the 25th Century. His last known comics work is
penciling and inking two short stories published in the May 1984 issues of two comics in Archie's
Archie Adventure Series imprint,
Blue Ribbon Comics #8 and
Steel Sterling #6. ==Personal life==