From John R. Salter, Jr. (HG), IUMM&SW:  THE GOOD, TOUGH FIGHT , MAINSTREAM,  October, 1960  (with up-dating notes):

"When it became obvious that management and right-wing   union pressure was not enough, the government moved in.

In 1952, the Senate Internal Security Committee, led by the late Pat McCarran of Nevada, and staffed by such worthies as J.B. Mathews and Harvey Matusow, hauled some of the most prominent Mine-Mill spokesmen before it in a futile effort to prove "Moscow domination"  in a IUMM&SW strike in which, ironically enough, it had been the mining concerns and not the union, who had refused to bargain.  The hand of the government was in Grant County, New Mexico, in late 1952 and early 1953, when Mine-Mill Local 890, led by Juan Chacon and Clinton Jencks, assisted a Hollywood group in filming "Salt of the Earth," based on the prolonged and successful IUMM&SW strike which had occurred at  Hanover, New Mexico the year before.   Intermixed with the burning of homes of union members, the brutal assaults on Mine-Mill officials and friends, and the formation of a vigilante committee which told union militants, "Clear out of Grant County in twelve hours or be carried out in black boxes," the U.S. Department of Immigration deported, on a minor technicality, leading lady Rosaura Revueltas to her native Mexico.  In 1954, Clinton Jencks, then an International Representative of IUMM&SW, was, on the flimsy and sketchy testimony of Harvey Matusow, convicted in a Dixiecrat courtroom in El Paso of perjuring himself on the non-Communist Taft-Hartley affidavits. Years later, Matusow announced that he'd lied, and eventually, in 1957, Jencks was released by the Supreme Court.  In 1954 again, the National Labor Relations Board attempted to strip, through de-certification procedures, the bargaining rights of IUMM&SW, charging that  Idaho-born Maurice Travis, at that time International Secretary-Treasurer, had committed perjury when he had signed the non-Communist Taft-Hartley oath.  The Supreme Court later killed this maneuver which, had it been successful, would have eventually led to the complete destruction of Mine-Mill.  Travis, however, was singled out in 1955, charged and eventually convicted of Taft-Hartley oath perjury.  He appealed and eventually received a new trial, at which he was again found guilty.(1)  In 1957, the Subversive Activities Control Board held almost half a year of hearings calculated to prove the "Communist domination" of the mine union.  The hearings were eventually recessed with no decision being announced. (2). . .The month of November, 1956 saw government authorities hand down indictments against thirteen top Mine-Mill staff members and Maurice Travis who had left the union some time before, charging them with "conspiracy to file false non-Communist Taft-Hartley affidavits" in the period between 1949 and 1956."  (3)

1)  This second Maurice Travis "perjury" case was thrown out by the U.S. Supreme Court in 1961.

2)  The U.S. Court of Appeals effectively killed this "proceeding" in 1965.

3)  The Mine-Mill "conspiracy case,"   brought initially by the government in 1956,  remained relatively quiescent for three years and was not brought to trial until the massive IUMM&SW-led industry wide copper strike  (from "Butte, Montana to the Mexican border" and some other places as well) took place in 1959 into 1960.  In what was obviously a deliberate case of planned management/government strike-breaking and union-busting, this sweeping conspiracy case was brought to trial  at Denver by the government  during the course of the copper strike itself -- thus tying up much of the time of the top IUMM&SW leadership and providing  anti-labor news media with daily  Red Scare  stories.   Mine-Mill won the extraordinarily hard-fought copper strike; but almost all of the Mine-Mill conspiracy defendants were convicted  on December 17, 1959 and sentenced to prison terms and heavy fines the following March.   In 1966, the U.S. Supreme Court threw out the so-called conspiracy convictions.   [See the above cited long article of mine (JRS/JHG), IUMM&SW: The Good, Tough Fight, for a discussion of Western Federation of Miners/International Union of Mine, Mill and Smelter Workers history with a primary  focus on the hard-fought 1959-60 copper strike and the accompanying Federal "conspiracy trial" attack on the union.]

In 1967, its fiscal resources cut to the bone  by its prolonged persecution at the hands of a thoroughly vindictive  United States government,  the International Union of Mine, Mill and Smelter Workers  merged with its old enemy, the United Steelworkers of America (whose leadership by this time included a few somewhat "better" faces than had previously been the case.)  A significant exception to  the merger was the Mine-Mill local at Falconbridge Nickel, Sudbury, Ontario which stubbornly refused to merge with Steel and which  has carried on into the new century a quite effective Mine-Mill existence as Sudbury Mine, Mill and Smelter Workers  Union, Local 598. (Since the mid-90s, it's been hooked-up with CAW, the growing 1985 Canadian breakaway from the U.S.-based United Auto Workers.)