During the college year 1842-1843 the Tau Delta Theta Society was organized at Dartmouth College with fourteen members, all from the Sophomore Class. It was small in numbers but well selected and managed. It moved on quietly, minded its own business, and did much good work. The next few years, however, found potent aspirations awakening within the bosom of the young society. In the autumn of 1844 it entered into correspondence with the Amherst Chapter of the Alpha Delta Phi, with a view of converting the Tau Delta Theta into a chapter of the Alpha Delta Phi. The Amherst Chapter seemed to favor such a change; but no definite results were reached. At the same time strenuous efforts were made to keep other Dartmouth societies uninformed as to the initiation and progress of the ambitious plan. For such was the state of inter-fraternity jealousy that every possible hostile influence was brought to bear on the group. Several times the negotiators resorted to long and tedious stagecoach trips to avoid the possibility of the mails being intercepted by the rivals. Continuous delay on the part of the Amherst Chapter only brought forth renewed effort from Hanover. Finally the petition was granted, and, conveyed by a delegation composed of Brothers from Amherst and Yale, the Charter arrived sanctioning the new Chapter of the Alpha Delta Phi.

The presence of the delegates in Hanover put an end to all doubts in the minds of both Tau Delta and their rivals. On a windy March evening in 1846 the installation took place in Professor Sanborn’s study (a room reproduced and preserved as a museum in Sanborn House), the charter was produced and signed, and Tau Delta Theta was formally evolved into the Dartmouth Chapter of the Alpha Delta Phi. With the same zeal that characterized its struggle for establishment, the new fraternity, quartered in its first-club rooms in old Dartmouth Hall, began its long career at Dartmouth. After being inactive and with its house closed during World War II, the Chapter reopened in March 1946 with some 15 Brothers returning (from the delegations of 1940 to 1947).

The Dartmouth Chapter became inactive in 1968.