A United States Treasury security is a government debt issued by the United States Department of the Treasury through the Bureau of the Public Debt.

Treasury securities are the debt financing instruments of the United States federal government, and they are often referred to simply as Treasurys.

There are four types of marketable treasury securities: Treasury bills, Treasury notes, Treasury bonds, and Treasury Inflation Protected Securities (TIPS).

There are several types of non-marketable treasury securities including State and Local Government Series (SLGS), Government Account Series debt issued to government-managed trust funds, and savings bonds.

All of the marketable Treasury securities are very liquid and are heavily traded on the secondary market.

The non-marketable securities (such as savings bonds) are issued to subscribers and cannot be transferred through market sales.

The U.S. government knew that the costs of World War I would be great, and the question of how to pay for the war was a matter of intense debate. The resulting decision was to pay for the war with a balance between higher taxes (see the War Tax Act) and government debt. Traditionally, the government borrowed from other countries, but there were no other countries from which to borrow in 1917: U.S. citizens would have to fully finance the war through both higher taxes and purchases of war bonds.

Alan Greenspan (/ˈælɨn ˈɡriːnspæn/; born March 6, 1926) is an American economist who served as Chairman of the Federal Reserve of the United States from 1987 to 2006. He currently works as a private adviser and provides consulting for firms through his company, Greenspan Associates LLC. First appointed Federal Reserve chairman by President Ronald Reagan in August 1987, he was reappointed at successive four-year intervals until retiring on January 31, 2006 after the second-longest tenure in the position.

Greenspan came to the Federal Reserve Board from a successful consulting career, holding political views influenced by Ayn Rand. Although he was subdued in his public appearances, favorable media coverage raised his profile to a point that several observers likened him to a "rock star". Democratic leaders of Congress criticized him for politicizing his office because of his support for Social Security privatization and tax cuts that they felt would increase the deficit. The easy-money policies of the Fed during Greenspan's tenure has been suggested to be a leading cause of the subprime mortgage crisis, which occurred within months of his departure from the Fed, and has, said the Wall Street Journal, "tarnished his image".