Alpha Tau Delta is a professional fraternity for persons in collegiate nursing. It was founded February 15, 1921, at the University of California and was incorporated the same year. Through the years more than 30 college chapters were organized.

The purposes of Alpha Tau Delta were: to further higher professional standards for the nursing profession; to inaugurate projects that strengthen the specific field of professional nursing; to develop character and leadership, encourage high ethical standards of professional conduct in which members may develop sound professional philosophies; to encourage excellence of individual performance and develop the highest possible scholastic attainments; to organize the social life of its members as a contributing factor in their educational program, and maintain an intrafraternity spirit of cooperation; and to form a close bond of friendship, fellowship, mutual helpfulness, and understanding among college students in the nursing profession.

Authorized college chapters conferred membership in the fraternity. There were two chapters at Montana State University: Lambda Chapter for academically qualified undergraduate nursing students, and Lambda Pi Chapter for alumnae.

The original charter for the Lambda Chapter was issued to Montana State College on April 27, 1940, when initiation and installation of members also took place. The first annual meeting appears to have been held on June 2, 1956. Divisions of Alpha Tau Delta were organized in Butte, Billings, Bozeman, and Great Falls. In 1982 Alpha Tau Delta was replaced at Montana State University by Montana's Zeta Upsilon Chapter of Sigma Theta Tau.

Lambda Pi Chapter was organized in 1963 with stated purposes: to inaugurate projects that enrich the individual alumnae and specific fields of professional nursing; to assist Lambda Chapter in their stated purposes; and to provide stimulation and guidance to Lambda Chapter. The alumnae chapter elected its own officers and held quarterly meetings.