[4] As of December 31, 2018[update], the average life of a dollar bill in circulation is 6.6 years before it is replaced due to wear.

The obverse was nearly identical to the Series of 1923 $1 silver certificate, but the Treasury seal featured spikes around it and a large gray ONE replaced the blue "1 DOLLAR."

The reverse, too, had the same border design as the Series of 1923 $1 bill, but the center featured a large ornate ONE superimposed by ONE DOLLAR.

A small number of these $1 bills entered circulation and the rest were kept in Treasury vaults until 1949 when they were issued in Puerto Rico.

This occurred with that year's passage of the Silver Purchase Act, which led to a large increase in dollar bills backed by that metal.

On the obverse, the blue numeral 1 was changed to gray and made smaller, the gray ONE to the right was removed, the Treasury seal was made smaller and superimposed by WASHINGTON D.C., and a stylized ONE DOLLAR was added over the treasury seal.

Special Silver Certificates were also issued as payment for Allied troops in North Africa about to begin their assault into Europe, being distinguishable from regular Silver Certificates by their yellow seals; unlike the Hawaii overprint series, the remainder of the design was left unchanged.

The inclusion of the motto, "In God We Trust", on all currency was required by law in 1955,[23] It was added over the word ONE on the reverse.

Production of one-dollar Federal Reserve Notes was undertaken in late 1963 to replace the soon-to-be obsolete $1 Silver Certificate.

The first change since then came in 1969, when the $1 was among all denominations of Federal Reserve Notes to feature the new Treasury seal, with English wording instead of Latin.

[25] The $1 bill became the first denomination printed at the new Western Currency Facility in February 1991, when a shipment of 3.2 million star notes from the Dallas FRB was produced.

Since 1933, the one-dollar bill has been the exclusive experimental denomination among circulating US currency (except for the Natick experiment in 1981, see below).

The first experiment was conducted in January and February of that year to assess the effects of using different ratios of cotton to linen in the make-up of the bills.

One-dollar bills were again the subject of experimentation in May 1992, when the BEP began to test a web-fed Intaglio printing press.

BEP-85-73 to procure a web-fed intaglio printing press to dramatically increase the production of currency notes within the confines of their current (1985) 14th & C street facility.

Because of mechanical problems and operator error, as well as the sometimes poor quality of the notes, production was ended in July 1996.

If "FW" appears before the lower right plate number it indicates that the bill was produced at the satellite Bureau of Engraving and Printing facility in Fort Worth, Texas.

The reverse of the one-dollar bill has an ornate design that incorporates both sides of the Great Seal of the United States to the left and right of the word "ONE".

This word appears prominently in the white space at the center of the bill in a capitalized, shadowed, and seriffed typeface.

The reverse of the seal on the left features a barren landscape dominated by an unfinished pyramid of 13 steps, topped by the Eye of Providence within a triangle.

At the base of the pyramid are engraved the Roman numerals MDCCLXXVI (1776), the year of American independence from Britain.

At the top[citation needed] of the seal stands a Latin phrase, "ANNUIT COEPTIS", meaning "He favors our undertaking."

At the bottom of the seal is a semicircular banner proclaiming "NOVUS ORDO SECLORUM" meaning "New Order of the Ages" that is a reference to the new American era.

The obverse of the seal on the right features a bald eagle, the national bird and symbol of the United States.

[30] In 1968–69 Joseph W. Barr was Secretary of the Treasury for only 31 days and his signature appeared solely on the 1963B dollar bill.

Some collectors thought that his brief tenure might make these notes valuable, but use of their plates continued for some time after his term in office and 458,880,000 were printed.

[32] Star notes may have some additional value depending on their condition, their year series or if they have an unusual serial number sequence.

[34] In modern times, the one-dollar bill is used much more than the dollar coin, despite the U.S. Government's repeated efforts to promote the latter.

The latest report claimed that switching to dollar coins would save $4.4 billion over thirty years.

[39] In response to various requests to redesign the $1 bill to include (among others) the Preamble, Bill of Rights, and list of Articles of the United States Constitution,[40] recent budgets passed by Congress have included provisions to prevent the Treasury Department from spending any of its funds to redesign the $1 bill, since the potential cost impact of this change on the vending machine industry would greatly exceed its benefits.