At the celebration of Dan Berrigan, S.J.'s 85th birthday (five years ago! Ad multos annos, Dan!) at St. Ignatius of Loyola parish in New York City, singer Natalie Merchant performed a classic union song, "Which Side Are You On?" The song, made more popular by Pete Seeger in the 1940s (but covered by many more, including recently by the Dropkick Murphys), was written by Florence Reece in 1931 during a United Mine Workers of America strike, after she and her family were terrorized by deputies purportedly hired by the mining company. 
Her husband, Sam Reece, was a union organizer during that strike; he died many years later of black lung disease, also known as "miner's lung."
Reece's song became a staple of union strike meetings and pro-worker rallies, and a favorite of the American political left for decades. Reece performed the song numerous times during the violent labor unrest in Harlan County, KT in 1973 (recounted in the Academy Award-winning documentary Harlan County, USA).
You can watch Merchant's performance here--the video quality is not great, but the lyrics remain poignant and pertinent eight decades after Reece wrote them.
Happy Labor Day!
