The following is a list of "scandals" that have led to calls for congressional reforms.

1854: Colt Patent Investigation

Samuel Colt wanted patent protection for his most famous invention, the Colt revolver. Lobbyists on behalf of Colt distributed guns and other gifts to gain senators' favor, according to Sen. Robert Byrd, D-W.Va., who in the late 1980s delivered a series of speeches about Congress' history with lobbying. Although a special House committee concluded that lawmakers had improperly accepted gifts, no action was taken.

1873: Credit Mobilier

Rep. Oakes Ames of Massachusetts tried to get his fellow lawmakers to vote in favor of railroad legislation. But it was his low-ball sale of Credit Mobilier stock in railroads — valued at $33 million — to his colleagues in the House and at Pennsylvania Avenue that caught the eye of investigators. He was censured, but not expelled because the conduct happened before he was elected.

1928-38: Boom, Then Bust

Big business boomed and then crashed, heralding the Great Depression. Following a similar wave, Congress started taking a harder look at lobbyists as public utilities began gaining economic strength and, through their lobbyists, political strength. While efforts to legislate new rules first failed, Sen. Hugo Black, who later became a Supreme Court justice, led the way to passage of laws that required lobbyists to register in order to deal with Congress.

1946: Lobbying on the Radar

After World War II, increasingly loud calls for lobbying reform did not fall on deaf ears. Congress adopted the Federal Regulation of Lobbying Act, which required registration with the House and Senate of any person "engaged for pay in attempting to influence the passage or defeat of legislation by Congress and the filing of reports on a calendar quarter basis." The law was later revised in the 1970s before being repealed and substituted by the Lobbying Disclosure Act of 1995.

1967: Adam Clayton Powell

Rep. Powell, a powerful African-American lawmaker from Harlem, N.Y., was excluded, or not permitted to take his seat in Congress, after an investigation found that as House Education Committee chairman, he had used committee money for personal travel and improperly authorized his clerk to pay his wife. Circumstances surrounding the investigation into him were tinged with racial controversy, and he won re-election to his vacated seat in 1969. The case, according to the "Encyclopedia of the United States Congress," was the impetus for giving permanent status and investigative and enforcement powers to the House Committee on Standards of Official Conduct, better known as the ethics committee.

1972-74: Watergate

While the scandal unearthed after the break-in at the Democratic National Committee headquarters was limited to the White House, campaign finance controls were tightened when it was learned that President Nixon's insiders controlled large sums of cash siphoned from political donors, some of which was used to pay for the break-in at the Watergate Hotel. Nixon resigned in 1974 rather than face the likelihood of impeachment.

1976-1978: "Koreagate," Sex Scandals

Reports surface that Tongsun Park, a Korean businessman -- who recently resurfaced in the United Nations Oil-For-Food investigation -- was caught by customs officials with a list of congressional members and dollar amounts labeled "contributions."

A Justice Department investigation revealed that Park had distributed money throughout Congress in the form of cash and campaign contributions in order to influence votes on key Korean issues, including U.S. troop levels in South Korea.

With Watergate barely over and congressional staffers claiming that lawmakers were using contributions to buy sex, Congress passed a number of reforms.

According to the "Encyclopedia of the United State Congress," the primary reform was the Ethics in Government Act, which called for financial disclosure by federal officials and placed new restrictions on the ability of former federal officials to lobby their old agencies. The law also created the ability to run investigations independently from the Justice Department under an independent counsel.

1978-81: Abscam

One senator and six members of the House were convicted on charges related to the FBI's Abscam investigation, a wide-reaching probe begun in 1978 by the Justice Department. Lawmakers accepted bribes from undercover agents posing as Arab sheiks who asked for political favors in return. The politicians were given prison sentences between six months and six years, and all but Rep. Michael Myers, D-Pa., either were defeated for re-election or resigned. In 1980, Myers, who refused to resign, was the first House member to be expelled since 1861.

1989-91: Keating Five

Charles Keating was executive director of Lincoln Savings and Loan Association, one of several banks at the end of the 1980s whose financial stability was collapsing. After a government takeover of the troubled bank, investigators learned Keating had also contributed $1.5 million to the campaigns of five senators — Alan Cranston, D-Calif., John Glenn, D-Ohio, John McCain, R-Ariz., Donald Riegle Jr., D-Mich., and Dennis DeConcini, D-Ariz.

Keating also had asked the senators who became known as the Keating Five for intervention in a federal probe on his behalf. The lawmakers met with federal officials to lobby on behalf of Keating.

Lincoln eventually was taken over by the government in a bailout that cost taxpayers $2 billion. After a Senate ethics committee investigation, McCain and Glenn were found only to have exercised poor judgment; Riegle and DeConcini appeared to have acted improperly, but no action was taken. Cranston was reprimanded after he was found to have violated Senate ethics rules.

1990-1997: Bouncing House Bank Transactions

The House Bank, a financial institution available to lawmakers in the House of Representatives since the 1800s, was forced to close in 1991 after it was found that several congressmen were abusing their accounts. A report by the General Accounting Office, now known as the Government Accountability Office, said that in one year ending in June 1990, House members had written 8,331 bad checks. Even after reforms were put in place that year, 134 members wrote 4,325 bad checks, 581 of which were written for more than $1,000.

The investigation led to a number of convictions, including those of five congressmen and one delegate after they left the House: Reps. Carl Perkins, D-Ky., Albert Bustamante, D-Texas, Carroll Hubbard Jr., D-Ky., Mary Rose Oakar, D-Ohio, Donald "Buz" Lukens, R-Ohio, and Del. Walter Fauntroy, D-D.C.

1992-1996: House Post Office Cashes In Stamps

The investigation into the embezzling of House Post office funds by the postmaster and the trading of post office stamps by lawmakers for cash eventually led to Rep. Dan Rostenkowski, D-Ill., who was sentenced to serve 17 months in prison on two counts of mail fraud. Investigators found he had used more than $600,000 in public money for his personal use.

1989-1997: Gingrich Attacks, Attacked

House Speaker James Wright, D-Texas, facing a withering attack led by Rep. Newt Gingrich, R-Ga., resigned his speakership in 1990. The charges by Gingrich included improper lobbying of government officials on behalf of a company in which Wright had an interest; taking a large royalty — 55 percent — on his book, "Reflections of a Public Man"; and exercising "undue influence" in federal officials investigating the savings and loan crisis.

The incident not forgotten, Gingrich — who assumed the House speaker position in 1995 after Republicans swept the 1994 mid-term elections — faced his own set of accusations lodged by Democrats. More than 80 in total, they included improper use of government resources, and, later, questions about a $4.5 million book deal advance, which he eventually returned. While nearly all the charges are dropped, he paid $300,000 to the House ethics committee for the cost of the probe. After the 1998 election in which Republicans suffered unexpected losses, a GOP rebellion ensued, and Gingrich, who had been re-elected to an 11th term, quit the House.

Sources: The Encyclopedia of The United States Congress; "Lobbying," by Sen. Robert Byrd; Facts on File World News Digest.