Before they removed the cash/in-person option on localbitcoins.com, that is what I used for many years to find buyers for the BTC and meet with them in person locally.
What are the current options to find BTC buyers (and sellers) for cash transactions in person?
Back in 2011, I used to use bitcoin-otc.com but I looked at it today and ther order book is practically empty.
After LBC removed in person cash trades, the market dried up a lot. The obvious alternatives in the aftermath were Paxful and LocalCryptos, although the number of offers is always disappointing. If you're not near a major metro area, it's tough.
You can check out this thread for some other ideas. Not all of them allow US traders:
Help: A list of LocalBitcoin alternatives (P2P marketplaces)