The number the developer gave in a press release was "20-30." I find that reasonable as a very large Facebook data center near me has a permanent staff of around 50. Keep in mind that these large DCs use contractors for the majority of the work, which unfortunately doesn't really help with employment because the contractors mostly come in from out of state (there is a HUGE temp labor market for traveling IT technicians and skilled crafts get hired mostly from big national outfits that just send whatever crew is available next). It is good for the hotel business though.

You have no idea how much maintenance is required. Just replacing hard drives, not even counting server repairs, new servers installation, network infrastructure installation and maintenance, power distribution, generator engineering, water treatment etc etc

And that's all stuff that they bring in out of state contractors for. I know, it sounds odd, but this is pretty normal for any large industrial site.

Once it's built, it basically runs itself.

You have a guard, some remote hands, maintenance, maybe additional security or two, times 4 for the various shifts. 30 sounds about right.

Even 20 years ago the datacenters I worked with often had fewer employees onsite than "visitors" - because they rented out racks.

You're confusing colos and first-party data centers. A colo mostly relies on its customers for installs and maintenance. Google, MS, FB, Apple etc own the entire building so all the functions are local: server install and maintenance, network install and maintenance, generator maintenance, electricians, water treatment in some cases... That's very easily in the hundreds if not thousands for big sites.

Count the cars here: 36.242186561973, -95.32619746715035

Yep, and anything outside of that is contracted groups that come in from outside. Maybe a hotel in the area would get a little more business, but it won't be much.

From the Maine Monitor:

[…]the data center would have employed only about 30 workers, the city estimated.