The Blob (1958)

Starring Steve McQueen, Aneta Corsaut, Earl Rowe, Olin Howland, Stephen Chase
Directed by Irvin S. Yeaworth Jr.
(actor & director credits courtesy IMDB.com)

A teenager and his girlfriend try to convince a small town's authorities that a growing monster that swallows people whole is genuine and threatening the town.

Although the special effects haven't aged well, this remains a charming and compelling film with memorable imagery for "The Blob" that later spawned a sequel and a remake.  The familiar message at the heart of the picture of teenagers not being respected or listened to by adults was not new when this film came out and was probably better presented in other films, but McQueen and Corsaut's performances as noble and decent young people sets the film apart.  McQueen of course went on to a distinguished career starring in some of the most highly regarded films of the 1960s and 1970s.  This was also the first of an interesting trio of science fiction pictures from director Yeaworth, followed by 4D Man and Dinosaurus!