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|Date Introduced||Rate for first ounce (USD) (Letter)||Rate for first ounce (Package)||Additional ounces||Postcard rate||Comments|
|March 3, 1863||.06 (.03 per half ounce)||.06||.06 (.03 per half ounce)||.02 per half ounce in drop boxes|
|March 3, 1883||.04 (.02 per half ounce)||.04||.04 (.02 per half ounce)|
|July 1, 1885||.02||.02||.02|
|November 2, 1917||.03||.03||.03||War Years|
|July 1, 1919||.02||.02||.02||Dropped back by Congress|
|July 1, 1928||.02||.02||.02||.01|
|July 6, 1932||.03||.03||.03||.01|
|January 1, 1952||.03||.03||.03||.02|
|August 1, 1958||.04||.04||.04||.03|
|January 7, 1963||.05||.05||.05||.04|
|January 7, 1968||.06||.06||.06||.05|
|May 16, 1971||.08||.08||.08||.06|
|March 2, 1974||.10||.10||.10||.08|
|September 14, 1975||.10||.10||.09||.07||Last surface mail rate|
|December 31, 1975||.13||.13||.11||.09||All domestic first class & postcards by airmail|
|May 29, 1978||.15||.15||.13||.10||A Stamp Used|
|March 22, 1981||.18||.18||.17||.12||B Stamp Used|
|November 1, 1981||.20||.20||.17||.13||C Stamp Used|
|February 17, 1985||.22||.22||.17||.14||D Stamp Used|
|April 3, 1988||.25||.25||.20||.15||E Stamp Used|
|February 3, 1991||.29||.29||.23||.19||F Stamp Used (also 4 cent F makeup rate stamp)|
|January 1, 1995||.32||.32||.23||.20||G Stamp Used (also 3 cent G makeup rate stamp)|
|January 10, 1999||.33||.33||.22||.20||H Stamp Used (also 1 cent H makeup rate stamp)|
|January 7, 2001||.34||.34||.21||.20||Nondenominated Stamps Used|
|July 1, 2001||.34||.34||.23||.21||Nondenominated Stamps Used|
|June 30, 2002||.37||.37||.23||.23||Flag and Antique Toy Stamps Used|
|January 8, 2006||.39||.39||.24||.24||Lady Liberty Flag Stamp Used|
|May 14, 2007||.41||1.13||.17||.26||Shape-based postage pricing introduced; Forever stamps introduced; different prices for letters and packages for the first time|
|May 12, 2008||.42||1.17||.17||.27||Price change announced February 11, 2008|
|May 11, 2009||.44||1.22||.17||.28||Price change announced February 10, 2009|
|April 17, 2011||.44||1.71 (3 oz)||.20 (letters)|
|January 22, 2012||.45||1.95 (3 oz)||.20 (letters)|
|January 27, 2013||.46||2.07 (3 oz)||.20 (letters)|
|.33||Price change announced October 11, 2012|
|January 26, 2014||.49||2.32 (3 oz)||.21 (letters)|
|.34||Price change announced September 25, 2013|
Taking the above data and plotting it yields the graph shown to the right. The dark plot is the nominal issued price of the stamp and the light plot is the price adjusted for inflation and is shown in 2008 US cents.
This plot shows that, despite the rise in the nominal cost of a first-class stamp, the adjusted cost of the stamp has stayed relatively stable. The large jumps in the early 1900s are because a change by a single penny was large compared to the cost of the stamp. For example, the price increase from $0.02 to $0.03 on July 6, 1932 was a 50% increase in cost. Additionally, while the cost of the stamp itself remained fixed, the adjusted price in 2008 dollars was not fixed over time which added to larger jumps in adjusted prices.
Domestic Parcel Post service was adopted in 1913, 25 years after the Post Office had agreed to deliver international parcel post packages pursuant to the Universal Postal Union treaty and various bilateral agreements with other nations. Initially, there were no or few postal regulations governing packages mailed by parcel post. To construct a bank in Vernal, Utah, in 1916, a Salt Lake City Company ascertained that the cheapest way to send 40 tons of bricks to the building was by parcel post. Each brick was individually wrapped and mailed. Postal rules were promptly rewritten.
Bulk postal rates were restructured in 1996:
In 2007, First Class Mail was restructured to include variable pricing based on size, not just on weight. Shape-based postage pricing is a form of dimensional weight. Also at that time, International Parcel Post air service was rebranded as Priority Mail International, and Parcel Post surface service was discontinued for international destinations.
Regular Air Mail service began in 1918 and over the years rates varied considerably depending on distance and technology. Domestic Air Mail, as a class of service, officially ended May 1, 1977. By that time all domestic First Class Mail was being dispatched by the most expeditious means, surface or air, whether or not the Air Mail postage had been paid.
Additional charges for Special delivery existed from 1885 to 2001. Today, Express Mail Overnight is the closest service.
During the summer of 2010 the USPS requested the Postal Regulatory Commission to raise the price of a first class stamp by 2 cents, from 44 cents to 46 cents, to take effect January 2, 2011. On September 30, The PRC denied the request, but the USPS filed an appeal with the Federal Court of Appeals in Washington DC.
On December 24, 2013, the USPS announced yet another increase in postal rates. Stamps will cost 3 cents more, increasing their price to 49 cents. Bulk mail, periodicals and package service rates will each increase by six percent. The increase is intended to make up for a 5 billion loss during the 2013 fiscal year. 
Unions of the U.S. Postal Service:
Beecher, Henry W. and Anthony S. Wawrukiewicz. U.S. Domestic Postal Rates, 1872-2011. Bellefonte, Pa.: American Philatelic Society, 2011. ISBN 9780933580787