"The militia of the United States consists of all able-bodied males at least 17 years of age and, except as provided in section 313 of title 32, under 45 years of age who are, or who have made a declaration of intention to become, citizens of the United States and of female citizens of the United States who are members of the National Guard. (http://www.law.cornell.edu/uscode/text/10/311)
Following that, the unorganized militia are the above minus those in the National Guard or the Naval Militia. Per modern interpretation of Federal law, this now probably includes women.
But the flip side is that attitudes today would not say that a woman "taking up arms" like men do is illegitimate. See, e.g., the one law that failed in the recent Colorado gun grabbing batch, that would have banned concealed carry at public colleges (note the minimum age for a licence is 21).
Women did not like being told they weren't fit to carry to defend themselves against rape and made a compelling case. Evie Hudak, the woman legislator who took point on the opposite side, had to resign so that she wouldn't be recalled like two previous state senators, replaced with a Republican, and flip control of the state senate.
n. An army composed of ordinary citizens rather than professional soldiers.
n. A military force that is not part of a regular army and is subject to call for service in an emergency.
n. The whole body of physically fit civilians eligible by law for military service.