@crdavis0902 I don't think there is a such configuration in the union tool but you can add some identifiers just before the union tool using a formula tool, make sure the identifier name is the same when you assign. Something like the attached workflow
If the data came from multiple Input Data tool, you can add file name into the dataset. Below is the configuration.
I'd also put record IDs (using a record ID tool) on each of the streams before hitting union - along with a dataset name (using a formula tool).
That's a very very common pattern, and an easy way to keep track!
@Dina idea of the filename on the input would eliminate the need for a dataset name.