Crossley, who joined the Magpies' youth set-up in 2020 from Morecambe, scored ten goals across all competitions for United's second-string during the 2023-24 campaign, including seven strikes in the Premier League 2.
He links up with National League North outfit South Shields, managed by former Newcastle United Under-21s Lead Coach Elliott Dickman, on a two-year deal.
Crossley told southshieldsfc.co.uk: "It's local to me and it was a very easy decision. Working with Elliott before made it a lot easier of a decision and I know a couple of the lads here.
"I've been on the phone to Elliott quite a lot this week about the plans, what he wants to do, and I've come here to enjoy it."
Ferguson, who joined Newcastle's Academy from Tranmere Rovers in the summer of 2021, spent the first-half of the 2023-24 campaign on loan at Scottish League Two side Forfar Athletic and joins the Scottish League One side on a one-year deal.
The Liverpool-born striker links up with Caley Thistle who are managed by his father Duncan, who spent two years at St. James' Park between 1998 and 2000.