Complex sentence: Negotiations on a merger had begun soon after the national bodies merged, but it took the personal intervention of AFL-CIO President George Meany to effect a merger in Pennsylvania leaving only one state, New Jersey, remained unmerged.
Split into simpler sentences: Negotiations on a merger began soon after the national bodies merged, but it took the personal intervention of AFL-CIO President George Meany to effect a merger in Pennsylvania. The merger meant that only one state, New Jersey, remained unmerged.