I don’t think many people could have foreseen the Sounders would be playing in CCC and the Cosmos would be playing in USL1 50 years on:

On April 9, 1976 — 50 years ago last week — Brazilian icon Pelé opened the Kingdome with appropriate panache. In the concrete dome’s sporting debut, the 35-year-old’s New York Cosmos met the Sounders in a North American Soccer League exhibition. It was an exhibition — “a public showing,” per Merriam-Webster — in size, scale and spectacle. A capacity crowd of 58,128 flocked to the Kingdome, smashing an attendance record for soccer in the United States. It was also the 14th-largest gathering for any Seattle sporting event, trailing 13 UW football games … only because some Kingdome seats had yet to be installed.