[bentley]

The first article I looked up was New Mexico, because I knew, as does anyone familiar with New Mexico history, that it became a state in January 1912 (before which it was a territory). Arizona also became a state, in February. I was surprised to find both described as states of the United States in this 1911 encyclopedia. I suppose the editors just made a confident guess? The last sentence of both articles is, “In June 1910 the President approved an enabling act providing for the admission of Arizona and New Mexico as separate states.”