Reference USA (now called Data Axle) is pretty darn good for finding companies by location, industry, and number of employees. Requires quite a bit of manual clicking to export batches of results unless you use a scraper (which is probably against the terms of service), but it's great just for identifying businesses and their owners.

If you're trying to build a list for an email outreach campaign, you'll probably need to also buy a paid list, use a scraper, or use an extension like hunter.io though. If you're just trying to find businesses that fit within some basic criteria, Data Axle/ReferenceUSA's cost can't be beat.

redacted‌^ another searcher challenged me to do this (for fun) and I wrote him a Python script that scraps LinkedIn company pages. It uses your personal LinkedIn credentials so you need to be a bit careful how fast/much you use it. Happy to share. DM me if you want to chat.