Holders of an Oxford SSO will find Westlaw US the most convenient subscription database for US federal legislation
However there are also reliable official sites on the free web available to all
Holders of an Oxford SSO can find US federal legislation as originally promulgated or published via
On the free web are
Federal legislation is published both chronologically and in codified form. The official codified version is the United States Code which was first published in 1926 and was preceded by the Revised Statutes of the United States. It should be noted that, unlike the coherent codes of civil law jurisdictions, the United States Code is a collection of separately enacted statutes which have been consolidated into a logical framework. Although the Code is compiled and published under the authority of Congress, only certain “titles” (the main subdivisions) have been enacted into positive law. For other titles, the Code is prima facie evidence of the law, but the authoritative text is that found in the individual acts as published in Statutes at Large.
The Library's extensive holding of US law includes old editions of series of legislation, shelved in the secondary collection on the ground floor of the Law Libary. This collection is open access to readers who have choice of lift or stairs. Shelf marks run from USA 010 to USA 045
For example the Law Library has
United States Code Call Number: USA 030 Editions of 1926, 1934, 1940, 1952, 1958, 1964, 1970, 1976, 1982, 1988, 1994, 2000
A codifiction of the general and permanent laws of the United States in force on the effective date of the edition. First published in 1926, with new editions in 1934 and then at six-year intervals, and with annual supplements in the intervening years. (The 1926 edition was published in Vol. 44, Part 1, of Statutes at Large.) Although published with congressional authorization, only certain titles (the main subdivisions) have been enacted as positive law.
Online sources for historic US legislation are:
Legislation and Statutory Interpretation, 2d by If you are writing a thesis or dissertation for the Oxford Law Faculty, follow US practice for the citation of primary sources (legislation, cases) - then apply OSCOLA's principles for consistency & clarity. (OSCOLA (4th edn, 2012) paras 2.8.1, 2.8.2)
The Bluebook : a uniform system of citation by 
ALWD Citation Manual: A Professional System of Citation by Federal legislation is published both chronologically and in codified form. The official codified version is the United States Code which was first published in 1926 and was preceded by the Revised Statutes of the United States. It should be noted that, unlike the coherent codes of civil law jurisdictions, the United States Code is a collection of separately enacted statutes which have been consolidated into a logical framework. Although the Code is compiled and published under the authority of Congress, only certain “titles” (the main subdivisions) have been enacted into positive law. For other titles, the Code is prima facie evidence of the law, but the authoritative text is that found in the individual acts as published in Statutes at Large.
