N.H. Const. pt. 2, art. 26
And that the state may be equally represented in the senate, the legislature shall divide the state into single member districts, as nearly equal as may be in population, each consisting of contiguous towns, city wards and unincorporated places, without dividing any town, city ward or unincorporated place. The legislature shall form the single member districts at its next session after approval of this article by the voters of the state and thereafter at the regular session following each decennial federal census.
June 2, 1784. Number of senators elected from each district (county) proportioned to taxes paid by each district.
Amended 1792 dividing the state into 12 senatorial districts still based on proportion of taxes paid by the district.
Amended 1877 increasing senate to 24 members from single member districts.
Amended 1964 providing for election of senators on basis of population.