Mass. Gen. Laws ch. 41 § 81A
Any city except Boston, and, except as hereinafter provided, any town may at any time establish a planning board hereunder. Every town not having any planning board shall, upon attaining a population of ten thousand, so establish a planning board under this section. A planning board established hereunder shall consist of not less than five nor more than nine members. Such members shall in cities be appointed by the mayor, subject to confirmation by the city council and in towns be elected at the annual town meeting or be appointed in such manner as an annual town meeting may determine; provided, that a town which has a planning board established under section seventy may, at an annual town meeting or at a special town meeting called for the purpose, vote to establish a planning board under this section and may provide that the members of the planning board then in office shall serve as members of the planning board under this section until the next annual town meeting. When a planning board is first established or when the terms of members of the planning board established under section seventy serving as members of the planning board under this section expire, as the case may be, the members of the planning board under this section shall be elected or appointed for terms of such length and so arranged that the term of at least one member will expire each year, and their successors shall be elected or appointed for terms of three or five years each as determined by the city council in the case of a city and by the town meeting in the case of a town. Any member of a board so established in a city may be removed for cause, after a public hearing, by the mayor, with the approval of the city council. A vacancy occurring otherwise than by expiration of term shall be filled for the unexpired term, in a city, in the same manner as an original appointment, and, in a town, if the members of the board are appointed, in the same manner as the original appointment. If the members of a planning board are elected, any unexpired term shall be filled by appointment by the board of selectmen and the remainder of the members of the planning board until the next annual election, at which time, such office shall be filled, by election, for the remainder of the unexpired term. All appointments pursuant to this section shall be in the manner provided in section eleven. Such a board shall elect annually a chairman and a clerk from among its own number, and may employ experts and clerical and other assistants. It may appoint a custodian of its plan and records, who may be the city engineer or town clerk. No member of a planning board shall represent before such board any party of interest in any matter pending before it.
Towns of less than ten thousand inhabitants, having no planning board established under this section may, by vote of the town meeting, authorize the board of selectmen to act as a planning board under this section until such a board is established; provided, that any such town, upon attaining a population of ten thousand, shall establish a planning board hereunder.
Mass. Gen. Laws ch. 41, § 81A