The Massachusetts Senate is the upper house of the Massachusetts General Court, the bicameral state legislature of the Commonwealth of Massachusetts. The Senate comprises 40 elected members from 40 single-member senatorial districts in the state. Descended from the colonial legislature, the current Massachusetts Senate was established in June 1780 upon the adoption of the Massachusetts Constitution. The first General Court met in October 1780 and consisted of one-year elected terms for both houses. This was expanded to two-year terms starting with the 142nd General Court in January 1921. The current delegation is the 187th General Court (2011–2012), consisting of 36 Democrats (D) and 4 Republicans (R).
In 1977 the Massachusetts Senate districts were redrawn, taking effect with the 171st General Court.
In 1987 the Massachusetts Senate districts were redrawn, taking effect with the 176th General Court.
In 1993 the Massachusetts Senate districts were redrawn, taking effect with the 179th General Court.
In 2001 the Massachusetts Senate districts were redrawn, taking effect with the 183rd General Court.
In 2011 the Massachusetts Senate districts were redrawn, taking effect with the 188th General Court.