(Minneapolis, MN) -- It's a sea of red t-shirts outside 14 Twin Cities hospitals as 12-thousand nurses hit the picket lines today for a 24-hour strike that's being called one of the largest nurses strikes in U.S history. Union spokesman John Nemo says staffing levels are among key points of contention. The hospitals say the union is asking for nurse-patient ratios that are used only in California and have not improved quality of patient care in that state. Among the Twin Cities hospitals that don't have striking nurses, Hennepin County Medical Center and Regions Hospital. Both hospitals have taken on additional patients. The strike officially ends at 7:00 a-m on Friday.