While researching a story on how Americans commit crime, we came across a disturbing fact. There's a significantly higher number of rape reports in Alaska than most other states.

Alaska has nearly 80 rapes per 100,000 residents, and South Dakota is a close second at about 70 rape reports per 100,000, according to the FBI's 2012 crime report. The next-highest is Michigan with 46 per 100,000.

Rape often goes unreported, so these statistics may be less reliable than other crime statistics. However, Alaska had a reputation for having a problem with rape before the FBI's recent crime report came out. In 2010 a poll of nearly 900 Alaskan women found that 37% had experienced sexual violence. This chart also shows how much Alaska has struggled with rape over the years.

How did Alaska get to be such a dangerous place for women?

Two possible causes are its high population of Native Americans — nearly 15% compared to the 1.2% national average — and its remoteness. South Dakota is also a rural state with a a high Native American population of nearly 9%.

Native Alaskans make up 61% of rape victims in the state, and Native Americans make up 40% of sex assault victims in South Dakota, The New York Times has reported. One in three Native American women has said she's been raped in her lifetime, according to a frequently cited Justice Department report from 2000. Native women are 2.5 times more likely to be raped than women of other races, that report found.

Nobody knows for sure why Native American women are so vulnerable to rape. Some experts blame alcoholism and the breakdown of the Native American family, The Times has reported. In the past, Native American tribes have not been allowed to prosecute non-Native Americans for raping members of their tribes, which also could have compounded the problem. (Obama recently signed a law that gives tribes more power to protect Native women, though.)

In very rural areas, like Alaska, women simply can't rely on police to come help them if they're raped. One 19-year-old Native Alaska woman who lived in a village of 800 called the police after a stranger broke into her home and raped her in the middle of the night, the Times reported in 2012. The police didn't answer, so she left a message. They never returned her call.

One study found that just 11% of rapes reported to the Anchorage Police Department between 2000 and 2003 led to a conviction. This lack of culpability could be another reason for the prevalence of sexual assault in Alaska. As one blogger in the state wrote, "Why is Alaska the rape capital of the U.S.? Because we allow it."