QUESTION: how would I find out the female prison population in Massachusetts in 1971, 1972, and 1973?

How and where would I find the number of women imprisoned in Massachusetts in 1971, 1972, and 1973? (I understand that the Massachusetts Department of Corrections had planned to phase out its female prisons by April 1973. If this did indeed happen, how would I find out the number of women sentenced to prison alternatives that year?)