 The Post Office has exclusive access to letter boxes marked "U.S. Mail" and personal letterboxes in the United States, but now has to compete against private package delivery services, such as United Parcel Service, FedEx, and Amazon.On March 18, 1970, postal workers in New York City—upset over low wages and poor working conditions, and emboldened by the Civil Rights Movement—organized a strike against the United States government.The strike initially involved postal workers in only New York City, but it eventually gained support of over 210,000 United States Post Office Department workers across the nation.