Much as the Founding Fathers had structured a Constitution whose promises of freedom and democracy sought to pull skilled European immigrants across the ocean, so their pioneer grandsons in the West evidently aimed to draw American women through the plains and over the mountains.

Data from the 1890 census provide some support for this admittedly crude theory. For every hundred native-born Wyoming males, there were only 58 native-born females. No other state had so pronounced a gender imbalance. Colorado and Idaho were the fifth and sixth most imbalanced states overall in 1890. The other early woman-suffrage state, Utah, had a somewhat higher percentage of women (thanks to its early experience with polygamy), but even Utah had only 88 native-born females for every hundred native-born males, ranking it 11th among the 45 states in the mid-1890’s. Also, the second, third, fourth, and seventh most imbalanced states — Montana, Washington, Nevada, and Oregon — would all embrace woman suffrage in the early 1910’s, several years ahead of most sister states. In all these places, men voting to extend the suffrage to women had little reason to fear that males might anytime soon be outvoted en masse by females (Amar, America’s Constitution, pp. 419-25).

You can read his entire narrative on the evolution of women’s suffrage here. Interestingly, Amar — who is not an empirical economist — was able to see a couple of additional legal/political wrinkles that others might miss:

Above and beyond any individualistic desire to woo women that may have motivated the men of Wyoming and other Western regions, federal territorial policy provided a modest if unintended spur to woman suffrage. In general, Congress in the 19th century waited for each territory to achieve a certain critical population mass before admitting that territory to statehood. Although Congress followed no single formula applicable to all places and all times, each western territory understood that rapid population growth would enhance its prospects for early statehood. Each new woman in the West would not only bring to a territory her own person but might also help produce future growth through childbearing. And if Congress ever decided to focus not on a given territory’s total number of inhabitants but rather on the size of its voting base, then woman suffrage would almost double the key number. …

Another aspect of the endgame: If and when women did get the vote, woe unto the diehard anti-suffrage politician who had held out until the bitter end! Each state legislator or Congressman from a non-suffrage state had to heed not just the men who had elected him, but also the men and women who could refuse to reelect him once the franchise was extended. (After ratification of the Direct Senate Election Amendment, every U.S. senator had to focus on the statewide voters rather than a tiny clump of political chums in the state capital.) The experience in Ohio, where male voters had refused to enfranchise women in 1912 and again in 1914, nicely illustrated the underlying electoral math. Senator Warren Harding voted for the Woman Suffrage Amendment and went on to capture the White House in 1920. Conversely, Senator Atlee Pomerene opposed the amendment and was voted out of office in 1922.

But the bigger picture is one of consilience: Two very different methodologies came to similar conclusions on a central question of how men democratically agreed to dilute their franchise.