There were three main factors, or so it says in The Americans, one is the drain of manpower into the army. Another on would be the Union occupation of food growing areas. The third one would be that there is no longer slaves to work the fields.

The prices grew rapidly! In 1861 the average family would spend $6.65 a month but by mis - 1863 they would spend $68 a month on food. In the 1863 there were many. Riots started because of food!