Kansas City's American Multi-Cinema, Incorporated, who had opened the first IN-MALL twin theatre in 1963, continued their cinematic innovation with the introduction of the world's first 4-screen operation or MULTIPLEX. Known as the Metro Plaza 4, it opened, in Kansas City, Missouri, in 1966. It was a freestanding operation.

AMC's second multiplex theater was built as part of Omaha, Nebraska's WESTROADS MALL. The Six West Theatres began business in January 1969. This IN-MALL operation was soon followed by the NorthTown Six, at Dallas, Texas' NORTHTOWN MALL.

Simultaneously, AMC was also building 4-screen multiplex operations. The earliest, an AT-MALL theater known as the Fashion Square 4, was built as an outparcel of Southern California's LA HABRA FASHION SQUARE. It opened for business in August 1969. This venue was followed by the Eastmont 4 Theatres, an IN-MALL multiplex that was installed in Oakland, California's EASTMONT MALL, in early 1971. In August 1972, the world's first seven-screen multiplex, the Southwyck 7 Theatres, began business as part of Toledo, Ohio's SOUTHWYCK CENTER.

During the 1970s, as the multiplex phenomenon developed onward, previously-existing single and twin theaters were often hastily -and crudely- spilt into smaller multiple venues. These so-called shoe box -or cracker box- operations did much to diminish the motion picture viewing experience. Dividing a larger theater into two or three would require much smaller screens. Also, poorly-soundproofed partitions between auditoria often leaked sound between viewing rooms.