This is the sort of question that is very difficult, if not impossible, to answer with any certainty. It is hard to know why people take the political stands that they do. For example, do so many white American voters dislike President Obama because he is black or because of his policy choices? Do poorer people vote Democratic because they want the government to take care of them or because they truly think the party has better policies? It is not at all easy to answer these questions. All we can do is to suggest possible answers.
Two possible answers for why the West was first to extend suffrage to women have to do with the fact that there were relatively few women in the West when suffrage was granted. (This illustrates the difficulty of this question—we know for certain that women were relatively few, but we do not know for certain how or if that impacted the granting of suffrage.) One theory holds that the men of the West did not feel that they would be threatened by the women’s vote because there were so few women in the West. We can compare this to the fact that states in the South, where African Americans were numerous, were much slower to grant them rights than states where the black population was lower. In this view, lower numbers of women made them less threatening to men and men were therefore willing to give them the vote. A second argument holds that the Western states granted women the vote as a way to attract more women. The lack of women in the West meant men had a hard time finding wives and it meant that there was likely to be more crime and violence and less stability. This theory says that Western men gave women the right to vote to make their states seem more attractive to potential female migrants.
Another theory argues that Western men gave women the vote in hopes of improving their societies. Some scholars argue that Western leaders who wanted to clean up their territories thought that women would vote for better policies than men would. For example, it is said that men wanted women to vote so that there would be a better chance to elect leaders who would build better schools and pay more attention to the needs of working people.
While some men wanted women to vote for better policies, other men are said to have wanted women’s votes to protect against something they felt was worse. The idea here is that these territories knew that black men could vote and they wanted the votes of white women to lessen the power of the African American vote. In this view, women’s suffrage was a way to combat black political power.
A final view on this subject has to do with the pioneer character of the West. In this view, the West was settled by hardy pioneers, both men and women. Women who came west had to play a much bigger role than women in the East. They had to do more to help around the family farm and they had to be tough enough to survive in difficult conditions. All of this made Western men more likely to respect women and to feel they deserved the right to vote.
Any and all of these explanations could contain at least part of the truth.
In my opinion, this is because women from western states were also the ones who called for women to also exercise the right to vote.