Divorces where the ex-wife gets the house, & the man moves far away. Oak Park, near L.A., is a well-known ‘Cougartown’ - the average household is a 40 - 50 something single mother with 2 - 3 kids. As the kids grow, most leave too - which leaves a town of mostly single moms. I would guess it was a family area ‘bedroom community’ in the 70s & 80s, then the wave of divorces.
With a skew like that one place to look would be the race and income stats. I would suspect (as one possibility) a heavily black economic underclass population is probably going to have substantially more female households in that age cohort and thus more countable female individuals in that cohort. I’d also look at the counting methodology if this is from US census they tend to miss men in borderline poverty situations with no fixed address.
If you sort the gender disparity by income what happens?
Because it’s a perfect community?