I am not sure which aspects you have concentrated on but hope this is, generally. more along the lines that you require:

Historically, women's participation in the vote was limited to a more child-like position of listening and learning without the capacity to make their own decisions although there were moves in the right direction as women gained the right to speak in public but could not get an amendment passed despite trying to combine their efforts with the abolition of slavery and the Black Man's right to vote; women, therefore remaining wholly disadvantaged and discriminated against. 

Eleanor Roosevelt was a champion for women's causes and human rights and a quote from her may help to center your argument:

The perpetual struggle of women's suffrage bears testament to the fearlessness and determination of women as, despite the many setbacks and the fact that voting was a punishable offence, they pursued their goal of equality in the eyes of the law and as Eleanor Roosevelt once said, "A woman is like a teabag...you never know how strong she is until you put her in hot water."

A thesis statement in an essay with a strong argument requires that you assert your viewpoint. Include your reasons in support of your argument. It is a good idea to have a starting point for your thesis statement but to adapt it as you go along as otherwise you are in danger of having to find information that fits with your thesis whereas, of course, your thesis supports your argument and is not intended to form the basis of the argument just the summary of it. It needs to sound factual because, according to your research, it is factual. The fact that others may disagree with your interpretation of the facts is all the more reason for your thesis to emphasize your position. 

Possibilities to consider whilst ensuring the "how and why" test might include:

Due to advances in equal rights, women's suffrage may sound like an outdated concept but, incredulously, still endures as policy makers are faced with bureaucratic decisions and State considerations, undemocratic formulas, limitations on voting rights which still exist and compliance with the US Constitution as the issues refuse to resolve themselves.  

Using a thesis statement similar to this should give your essay direction and maintain focus on the arguments as the following paragraphs will tackle bureaucracy which can include the State considerations and undemocratic formulas, voting rights and the US Constitution but all in terms of your specific argument. 

Another consideration could be:

Women have rights today thanks to the suffrage movement and the tireless efforts of many supporters but this has also led to a complacency in the modern era which is not commensurate with the enormous amount of effort, suffering and courage just to obtain the vote for future generations of women, even if limitations were and still are, imposed creating stereotypes that hamper many aspiring women's beliefs in themselves and their self-worth.  

The paragraphs that follow will give an in-depth view of the suffrage movement, supporters past and present and the effects of limitations such as they did and perhaps do exist, real or imagined, due to prejudice or one's own perceptions.