York went ahead after only three minutes as Josh Carson broke free to fire a deflected shot into the net and put his side 1-0 up.
They then continued their great start to the match by converting again less than 10 minutes later following Wes Fletcher's 12th-minute effort, after poor goalkeeping from the away side.
The home side were not done yet as they made it 3-0 in the 20th minute, with Ryan Brobbel's shot taking a lucky deflection to evade the helpless United keeper.
Brobbel popped up again in the 40th minute to provide his side with their fourth goal of the evening.
Scunthorpe did manage to pull one back after the break through Sam Winnall who crashed his effort into the top corner from inside the box, but it was too little too late as the home side took an easy three points.