This month marks the 100th year anniversary of Congress passing the 19th Amendment in 1919, affirming women’s right to vote. However, prior to that date, some states approved women’s suffrage before it became an amendment to the U.S. Constitution.

Harvard Business School historian Nancy Koehn joined Boston Public Radio Tuesday to give more background into how individual states played a part in the women’s suffrage movement.

“It was really literally a checkered map of women’s rights differing from state to state, with a great number of states having no women suffrage until the ratification of the 19th Amendment,” Koehn said.

Koehn explained how West Coast states outnumbered East Coast states in granting women voting rights.

“In many many ways at a state level, the west led the east," she said. "Interestingly, the first states really to grant women full suffrage at a state level were states like California.”

Even though the East Coast was home to key figures like Elizabeth Cady Stanton, Susan B. Anthony and Margaret Fuller championing the women’s suffrage movement, states on the east were slow to grant women the vote, Koehn noted.

“Massachusetts [and] New York were some of the very last states to do so at a state level," she said. "They were real holdouts in what became a huge push on the part of suffragettes to try and get New York, and other largely populated East Coast states, to approve women’s suffrage.”

Women had partial suffrage in some states, Koehn explained, with some states allowing women to vote in presidential elections, but not municipal elections. Yet some states out west granted full suffrage rights, Koehn said.

“Earlier in the west, as early as 1896, for example, in Idaho, 1893 in Colorado, and 1869 in Wyoming, women could vote in every election,” she said.

So why did the West lead its East Coast cousins? Koehn thinks that part of the reason has to do with western states having less historical baggage.

“It does seem that these states had interest very early on in creating a kind of more level playing field politically. None of these states were ever slave states so they didn’t have the terrible baggage and hypocrisy of slavery on their books. They were states that were settled later than other states, so I think there was probably a less entrenched social hierarchy certainly in California, Wyoming and places like that,” she said.

Koehn is an historian at the Harvard Business School where she holds the James E. Robison chair of Business Administration. Her latest book is “Forged in Crisis: The Power of Courageous Leadership in Turbulent Times.”