Go to the GPAA home page and scroll down to the bottom. Click on Chapters. A map of the United States will come up. Click on the state nearest you and you will find the chapters for that state. At this time I do not see any Chapters for Nebraska, so your best bet would be another state.
You may have members that live in your area to help you out. Its a holiday weekend and they may all be out prospecting !
Palmer Lake, CO