Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 35, § 27A

The county treasurer of each county shall act as the treasurer and custodian of the funds of every institution, organization, board, commission or other public body to the use of which funds of his county are contributed, provided that in case any such public body serves a district comprising more than one county, the county treasurer of the county in which such public body is chiefly located or has its headquarters, as determined by the director of accounts, shall so act.