The equity value of the offer is about $1.16 billion, based on 12.1 million Deltic's diluted shares outstanding at June 30.
Potlatch's offer values Deltic at $95.4 per share, representing a premium of about 7 percent.
The combined company will have capacity of 1.2 billion board feet with capacity heavily weighted towards high-margin southern yellow pine lumber.
The combined company is expected to have a pro-forma market cap of about $3.3 billion and a total enterprise value of more than $4 billion, including about $700 million in net debt, the companies said.
After the deal, Potlatch shareholders would own about 65 percent of the combined company, which would be named PotlatchDeltic Corp, while Deltic shareholders would own the rest.
Reuters had reported the deal on Sunday. The deal could offer more scale to cope with price volatility in the market.
Deltic Chief Executive Officer John Enlow would be the combined company's vice chairman, while Potlatch Chief Executive Officer Mike Covey would continue in the role.
Potlatch increased its annual dividend to $1.60 per share from $1.50.
BofA Merrill Lynch was the financial adviser for Potlatch, while Goldman Sachs & Co LLC was advising Deltic.
Deltic's shares were up 7 percent at $95.39 in premarket trading.