Complex sentence: It was one in a series of tornadoes that hit Southeast Minnesota that day, causing at least 37 deaths and over 200 injuries, and was the impetus for the creation of the Mayo Clinic.
Split into simpler sentences: It was one in a series of tornadoes that hit Southeast Minnesota that day. It caused at least 37 deaths and over 200 injuries, and was the impetus for the creation of the Mayo Clinic.