Two of the three NASL teams taking part in the Open Cup advanced past the fifth round of the competition.
The New York Cosmos were the only participating NASL side not to find victory, going down 2-1 to the Philadelphia Union at PPL Park.
"This is a tremendous accomplishment for the Carolina RailHawks and Atlanta Silverbacks and the League as a whole," said NASL Commissioner Bill Peterson. "All of our clubs have shown tremendous heart and skill as they have progressed through the Cup and tonight, while the New York Cosmos came up just short, it has been great soccer. The NASL's run in the 2014 US Open Cup will continue with a pair of tough Quarterfinal matchups our clubs will host on July 8 or 9. They will be ready."
The NASL v. MLS quarterfinal encounters will be highlighted by Carolina RailHawks, who emerged with an exciting extra time goal to get past LA Galaxy in Round 5, hosting FC Dallas as they put their 23 game home-unbeaten steak on the line. The Atlanta Silverbacks, who held on for a 2-1 victory with eight men in the field, will host the winner of Wednesday night's Chicago Fire against Columbus Crew match.