Limiting this question to federal laws certainly makes things easier!
Here is the significant federal legislation passed in the past century
on campaign finance:
1910 -- Corrupt Practices Act requires disclosure of contributions in
1925 -- Corrupt Practices Act amended to cap spending in U.S. Senate
general-election campaigns but it was widely criticized for having
1939 -- Hatch Act prohibited federal employees from donating to
1943 -- Smith-Connally Act sharply restricted campaign activities of
labor unions. (Unions later found ways around some of the rules.)
1947 -- Taft-Hartley Act further restricted campaign activities of
unions, corporations and interstate banks.
1971 -- Federal Election Campaign Act (FECA) expanded rules on
disclosure, limited some champaign spending, and provided limited
funding for campaigns. This law forms the framework for the law
1974, 1976 -- FECA amended, mostly in response to court decisions that
found parts of it violated the First Amendment guarantee of free
1979 -- More FECA amendments, mostly to make it more manageable.
Resources used in this summary:
A Brief History of Money in Politics
This page lists dates of major legislation and court decisions
affecting campaign finances.
Follow the Money
This page provides another list of major legislation and court
Federal Corrupt Practices Act of 1910, Revised 1925, Replaced 1971
This provides details on federal legislation, especially the 1971 law
Campaign Financing: Highlights and Chronology of Current Federal Law
This page includes a list of some of the minor pieces of legislation
(such as appropriations) that had some effect on campaign financing.
Numerous campaign finance reforms have been considered since 1979, but
anything significant has gotten bogged down in politics. One of the
stronger pieces of legislation seriously considered is the
McCain-Feingold bill. You can find numerous articles on that bill
using this Google search:
search term: federal election campaign reform feingold mccain
You may also be interested in the following page:
Campaign Finance Law 98
This page provides a summary of state laws affecting campaign
I hope this fully answers your question.
Google search term: campaign finance laws chronology 1925