Is there a way to create a set of pre-defined options / pick list on the forms?

Is there a way to create a set of pre-defined options / pick list on the forms? I have quite a few forms that reference the same group of individuals, that it would be much easier to update the pick list. If this is possible, when updated, would I have to go in and update each form's pick list or would it automatically replicate anywhere that is chosen?

Yes, it is possible. You can refer to our guide below for the process:

https://www.jotform.com/help/71-Prepopulating-Fields-to-Your-JotForm-via-URL-Parameters

The below application will help you create the URL:

http://prepopulate.jotform.io/

This would need to be manually updated on each form. But if you are looking at automatically prepopulating one form from another form's data, you can also check our guide below:

https://www.jotform.com/help/351-How-to-Automatically-Pass-Form-Data-to-Another-Form

Thank you, but for instance if you chose a single choice option you can select US States, Gender, etc. I was looking to create my own list.

I am not sure if I understand your query correctly. Do you want to create your own list in the single choice field, it is possible. Please refer below screenshot. You can add your options in the Options section.

Do you want to prepopulate the options in the single choice fields in one form to other forms? If yes, you can do that using the below guide:

Prepopulating-Fields-to-Your-JotForm-via-URL-Parameters