SAVANNAH, Ga. (AP) -- International Paper Co. said Thursday that it would close two Georgia paper mills, including one that has been a cornerstone of Savannah's economy for 90 years.

The company, based in Memphis, Tennessee, said it would stop making cardboard in Savannah and Riceboro by the end of September. The company will lay off about 800 employees in Savannah and about 300 employees in Riceboro, according to company statements and filings with state regulators.

The announcement came on the same day that the company said it would sell its pulp division to private equity firm American Industrial Partners for $1.5 billion. International Paper had previously announced it would consider a sale to focus the company solely on its packaging business. The sale is expected to close by the end of the year.

International Paper also said it would spend $250 million to expand production of cardboard at a mill in Selma, Alabama.

International Paper will take a $700 to $900 million accounting charge to reflect the reduced value of the cellulose fiber business. The pulp is used in towels, tissues and as absorbent filler in diapers and other personal care items. Some specialty pulp is also used in construction materials and paints.

Closing the two mills will reduce International Paper's capacity to make containerboard by 1.43 million tons (1.30 million metric tonnes). The company will write down the assets of the two mills by $570 million and expects to spend $158 million on severance payments and other closure costs.

The company says its trying to increase sales and profit by simplifying operations. International Paper has said that it's the largest maker of containerboard in North America, but that's it's trying to reverse a trend of decreasing profits and market share.

"While difficult, these decisions are essential to positioning International Paper for long-term success, enabling us to focus on the geographies, customers, and products where we can create the most value," Executive Vice President Tom Hamic said in a statement.

Earlier this year, International Paper closed a mill in Campti, Louisiana, laying off 470 people. Last year, the company closed a 675-worker mill in Georgetown, South Carolina.

The Savannah mill was built in the mid-1930s by what was then Union Bag and Paper, with jobs helping to ease the impact of the Great Depression on the coastal city. The mill in Riceboro, south of Savannah, opened in 1968 and was acquired by International Paper when it bought British papermaker DS Smith earlier this year.

Savannah Mayor Van Johnson said he was "devastated and disappointed" by the decision. Savannah Economic Development Authority CEO Trip Tollison called it a "terribly sad day for Savannah."

Georgia state House Speaker Jon Burns, a Newington Republican whose family has long worked in timber growing and logging, said effects would ripple beyond millworkers to loggers and timberland owners.

"These mill closures will undoubtedly deal a devastating blow not only to Georgia's timber industry but to the economic fabric of the entire southeast Georgia region," Burns said in a statement.