 Additional rivals were formed in the 1930s but the first serious rival was the National Postal Clerks Union (NPCU) that began in 1958 and by 1970 reach the membership of 80,000.Merger discussions dragged on for years, until the NFPOC, UNMAPOC and others merged in 1961 as the United Federation of Postal Clerks.Another round of mergers in 1971 produced the American Postal Workers Union (APWU).