County functions were assumed by the State of Massachusetts in 1998. Hampden exists today as an historical and geographic region.
On the 24th of June, 1811 the Northern portion of Hampshire County succeeded in its endeavors for it to be set off as a distinct county, with the name of Franklin, and with Greenfield as its shire town, though Cheapside, in Deerfield, was the favorite location for county houses, among the majority of the towns. The existence of county buildings in both Springfield and Northampton, and the increase of legal business in consequence of the increase of population, soon afterwards excited a movement in the southern part of Hampshire for still another division. On February 25, 1812, the division was effected by the establishment of the County of Hampden, with Springfield as the county seat. Old Hampshire was thus divided into three counties — the middle county, with Northampton as the shire town, retaining the time-honored name by which the whole of Western Massachusetts was originally known.