The port says Microsoft plans to build a data center that will employee about 100 people.
The Seattle Times reported that Microsoft already has a data center in the small town of Quincy, as do Yahoo, Dell, Sabey, Vantage, and Intuit. The companies have been attracted by relatively low electricity costs.
While the centers have boosted Quincy's economy, some residents have worried about air pollution from diesel-powered backup generators.
The newest data center is the second in Quincy for Microsoft, which built its first one there on port property in 2007.
The port says the deal is expected to close in late January.