Justice League of America #244 Newsstand

"The Final Crisis"

As the Infinitors and JLA fight vs. both Commander Steel and Mekanique on Earth-1 in JLA's Detroit headquarters, the JSA appears, searching for the missing Infinitors from Earth-2, and join in the battle, quickly defeating Mekanique (while strangely remembering her visit to them in 1942). Mekanique, damaged, then disappears back into the past. Meanwhile, as the Crisis rages on Earth-1, the JLA/JSA/Infinitors aid the people of Detroit as the world's in chaos around them, while Steel fights and defeats his grandfather in solo combat.