How many people can Wrigley Field hold?
Wrigley Field can hold somewhere in the 41,000's.
It depends on the stadium. Some MLB stadiums can hold up to 50,000 people at a time, such as Giants or Yankees stadium. Some stadiums are very small, such as the Houston Astro's field, which can only hold just over 25,000 people. I would say the average amount of people a baseball field can hold is around 35,000 people.
Did Sha Na Na play at Wrigley Field? Yes. Sha Na Na played Wrigley Field, along with Chuck Berry after a Cubs game. You paid for the Cubs game and the double-bill concert afterwards was free. During the concert many fans got overly-excited, went over the walls, and started dancing on the field. It was roughly sometime around 1984 (+/- a few years.)