Has mt st helens erupted before 1980?

Answer 1

Yes, many times.
Most recently prior to 1980 was a 57-year eruptive period that started in 1800 was named after the Goat Rocks dome, and is the first time that both oral and written records exist of Mount Ste. Helens erupting.

Answer 2

Yes, Mount St. Helens has had several minor eruptions prior to its major eruption in 1980. The most notable eruption before 1980 occurred in 1857.