ST. GEORGE — The cost of mailing a letter is going down for the first time in almost 100 years, and the U.S. Postal Service is introducing a new line of stamps honoring the National Park Service centennial.

The last time postal rates went down was on July 1, 1919, when postage dropped from 3 cents to 2 cents. But Sunday, the price of a first-class stamp drops 2 cents, to 47 cents. Commercial and other postage rates are going down as well.

A complete listing of new postage prices, effective April 10, is available at USPS online.

The price reduction is mandated by the Postal Regulatory Commission because of an expiring surcharge that was put in place in January 2014 to help the beleaguered Postal Service recoup $4.6 billion in losses dating back to the Great Recession. However, the Postal Service said in a news release Thursday, this amount only partially offsets Postal Service revenue losses — which the Postal Service estimates exceeded $7 billion in 2009 alone.

The service said the forced rate reduction will make Postal Service losses worse, estimating the service will lose $2 billion in annual revenue.

“Given our precarious financial condition and ongoing business needs, the price reduction required by the PRC exacerbates our losses,” Postmaster General and CEO Megan J. Brennan said.  “This unfortunate decision heightens the importance of the review of our ratemaking system which our regulator is required to conduct later this year.”

The Postal Regulatory Commission has authority to modify the U.S. postal system or create a new system. It is obligated to conduct review of the regulatory system in December, the scope of which the postal service is asking the commission to clarify in advance. See the petition filed Thursday here: USPS Petition to Regulatory Commission to Define Scope of 10-year Review.

According to the Associated Press Friday, in the Postal Service’s latest financial report, it showed a $307 million profit between October and December 2015, due in part to increases in holiday shipping. Postal officials said at the time that without the postal surcharge, they would have had a net loss of approximately $700 million in the first quarter.

The Postal Service relies on the sale of postage, products and services to fund its operations, its news release said. Although regulated, it serves as an independent agency and does not use taxpayer money for operating expenses. It cannot raise prices above the rate of inflation without the regulatory commission’s approval.

The service is appealing to Congress for help.

The service is asking Congress reinstate and make the 2014 surcharge permanent. It is seeking a congressional mandate to pre-fund retiree health benefits, the Associated Press reported Friday, something neither the government nor private companies are required to do. And it is asking Congress to give it more flexibility in setting rates.

“To properly compete for customers and continue to meet America’s evolving mailing and shipping needs, the Postal Service needs the financial capability to invest in the future,” Brennan said.  “We continue to seek legislative reforms to put the Postal Service back on a sustainable financial path, and pricing is an important component.”

New national parks commemmorative stamps

The Postal Service is celebrating the National Park Service’s 100th anniversary by releasing 16 stamps, each featuring a national park. One of the stamps already previewed is the Arches National Park stamp.