In addition to rules for proper citation of treaties, The Bluebook: A Uniform System of Citation identifies, in Table T4 and Rule 21.4.5, the preferred sources for U.S. treaty texts. Fortunately, most of the treaty sources listed below are available via Hein Online, especially in Hein's U.S. Treaties and Agreements Library (see the Treaty Publications tab), for at least some date ranges. Links are provided below.
Official U.S. Sources
United States Treaties and Other Agreements (U.S.T., bound volumes containing TIAS agreements), 1950 until approximately 1984
Previously, United States Statutes at Large (Stat. citations), published in volumes of U.S. session laws from 1778 - 1949
Treaties and Other International Acts (T.I.A.S.), 1945 - date (TIAS number assigned to each agreement); Hein Online provides TIAS agreements from 1982; the State Department web site provides online from mid-1990s
Previously, Treaty Series, 1778 - 1945 (arranged by TS locator number)
Executive Agreement Series,1929 - 1946 (arranged by EAS locator numbers; this series was replaced by T.I.A.S.)
Senate Treaty Documents (1981 - 2015) [see the box to the lower right]
Senate Executive Documents (1778 - 1980)
Intergovernmental Treaty Sources
United Nations Treaty Series (U.N.T.S.), 1946 to date
League of Nations Treaty Series (L.N.T.S.), 1920 - 1945
See The Bluebook, Table T4.2 for regional intergovernmental treaty sources.
Unofficial Treaty Sources, including:
International Legal Materials (I.L.M.), 1962 - date (available on Hein Online until last 3 years; more current texts available via Westlaw and Lexis)
Hein's United States Treaties and Other International Agreements, 1984 - date (Hein's KAV number)
Lexis Advance: Finding Treaties on Lexis
Westlaw's U.S. Treaties and Other International Agreements (searchable collection of treaties; from 1778 - )
See The Bluebook, Table T4.3 for other unofficial treaty sources.