The proper Monitor is your TV.

In 1979, apple hadn't introduced a monitor. They introduced the Monitor /// in 1980, so I guess that is the closest. The next best would be a Monitor ][, they came out in 1984 and were retrospectively intended to be the monitor of the ][ line.

EDIT- I use an Apple Monochrome Monitor with my IIe, it gets the job done just fine for fiddling with BASIC and such.(My first venture into programming... WOOHOOO)