In World Without Stars, Captain Argens tells Hugh Valland that they will be dealing with some Yonderfolk, i.e., extra-galactics. Valland asks. "'Like M 31?'" (Chapter II, p. 12) Googling reveals, to my surprise, that this is the Andromeda Galaxy.
When James Blish's John Amalfi discusses traveling between galaxies, he says that the nearest, apart from Andromeda, is NGC 6822, about a million light years away. See here. Knowing that both Valland and Amalfi had referred to another galaxy, I had to check whether it was the same one. Intergalactic sf is rare. It is good to read about journeys not to Mars or Proxima Centauri but to M31 and NGC 6822.