When nine U.S. citizens were killed in a brutal attack in northern Mexico last week, much of the world learned for the first time about that area’s past and prevailing ties to Mormon polygamy.

Those ties include a complex cast of characters and creeds — both mainstream Latter-day Saints and breakaway believers.

Helping to untangle and understand this web is historian Barbara Jones Brown, executive director of the Mormon History Association who has studied and written about post-1890 Mormon plural marriage.