The investments at 11 sites should create 35,000 temporary construction jobs and 12,000 permanent jobs, chief executive Darren Woods said in a speech at CERAWeek, the world's largest gathering of energy executives.
Some of the expansions began in 2013, but the scope of the project is now growing and the timeline extended, Exxon said.
Woods ran Exxon's refining division before becoming CEO two months ago, and the new spending benefits a sector with which he has significant experience and comfort. Investments in the high-margin projects should help ease concerns from Wall Street that Exxon's growth potential - especially in oil and gas exploration and production - is sliding.
"Exxon Mobil is building a manufacturing powerhouse along the US Gulf Coast," Mr Woods said. "These businesses are leveraging the shale revolution to manufacture cleaner fuels and more energy-efficient plastics."
The investments across Texas and Louisiana will take advantage of cheap shale gas to make plastics and other chemicals for export. The strategy builds on prior steps Exxon and peers, including Dow Chemical Co, have taken in the wake of the American shale expansion, which sharply cut production costs.
"The supply is here. The demand is there. We want to keep connecting those dots," Mr Woods said.
Exxon last month pledged to boost this year's spending by 16 per cent to expand operations, especially in shale production, after the company posted a better-than-expected quarterly profit, helped by rising oil prices and lower costs.
US President Donald Trump, who tapped former Exxon CEO Rex Tillerson for secretary of state, praised the company's spending plans as an example of "a true American success story". Most of the permanent jobs are expected to pay more than $100,000 per year.
"This is exactly the kind of investment, economic development and job creation that will help put Americans back to work," Mr Trump said.
The bulk of the expansion will take place in Beaumont, Texas, with plans to expand polyethylene production, oil refining capacity and liquefied natural gas exports.
Exxon also will increase its lubricant manufacturing capacity and potentially build a new refinery to produce ethane, a key building block for chemical production.
Mr Woods spent the larger part of his speech discussing climate change, an area for which Exxon has come under attack in the past year. The global economy can grow while also improving the climate, he said.
"I believe the assumption that affordable energy and a cleaner environment are a zero-sum game is mistaken," he said. "It underestimates the power of technology."
Mr Woods highlighted Exxon's research into carbon capture sequestration, biofuels and other areas as ones helping the company expand its operations beyond oil and gas.
"The only way to keep winning in a competitive market is to keep innovating," he said.
Hoping to stem at least some of the environmental controversy, Exxon in January, just after Mr Woods became CEO, named an environmentalist to its board of directors.
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