The original 747-100 and -200 was indeed designed with an upper deck lounge. The flight deck was placed above the main deck to facilitate cargo on the freighter models, and the upper deck was extended back to reduce drag. The earlier 377 Stratoliner had a below-deck bar, so Boeing decided to use the extra space for the lounge. After the oil crisis, most of the lounges were converted to first-class seating.

Source: Air & Space Magazine "How the 747 Got Its Hump"