ALBANY, N.Y.—State officials offered Amazon.com Inc. $800 million more in incentives than was previously known to win its second-headquarters contest and were even prepared to pay part of some employees’ salaries if the tech company developed a campus in New York.

Documents reviewed by The Wall Street Journal show the scope of what state and local officials initially put on the table as part of the 2017 HQ2 competition, in which more than 200 cities submitted bids to host a facility that Amazon said would house 50,000 jobs.

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