Using our WooCommerce USPS shipping plugin you can set up multiple 'ORIGIN' Zip Codes at the Product level.
As an example l have set up two products in WooCommerce
1 to ship from 08360 > Blue Bag
2 to ship from 90210 > Pink Hat
In the Orders page l can see that l have two products shipped from different locations.
On the WooCommerce orders page you will see this:
When you visit the USPS generate label page, you will notice that there are two labels that will be generated.
You will only need to to click the "Generate Label" once. Two separate labels will be generated.
Label generated for 08360
Label generated for 90210