There are three general types of reports: a) House and Senate Reports (deal with proposed legislation and issues under investigation); b) Senate Executive Reports (treaties and nominations); and c) conference committee reports (differences on legislation between the House and Senate have been committed to conference committees to work out a settlement). For legislative history research, a committee report is an essential document because it explains the text of the bill and reasons behind the legislation.
LoC American Memory web site: 1823 – 1873
Proquest Legislative Insight: 1929 - forward (in progress) for legislation that became law.
CIS fiche set (UES in law library): 1970 - date
LexisNexis (HMTL): 1990 - date