County history books are available for most if not all counties in the United States. These books typically cover subjects from the physical landscape of the county to its very early history to the founders of the villages in the county to prominent individuals and families. When you're able to find your ancestors listed in one of these books, it will typically tell at least the region they came from before arriving in the county, their occupation, their immediate family and the life they lived. Many times it will also provide a bit more information on the individual's parents and grandparents and children and grandchildren. This can prove to be a huge help if you don't already have this information.
It used to be that you'd have to find these books in the library or historical museums of the area. Several years ago, I was shocked to find a copy of the History of Lake County, Indiana in a local used book store! It cost me $50 but I considered that a bargain considering the distance I live from Indiana. This is the area my Bixenman family settled in and where my great-grandmother, Philomena Bixenman was born just before her family moved on to Chariton County, Missouri. Now you can download the entire book for free!
It's very easy to find the book your ancestors are from. Just go to www.google.com and search for (the county name) (state) history. ie "Lake County Indiana history". Typically, you'll be able to find the book on both archive.org and Google Books. I've added the county histories of all my ancestors to my Google Play account. This way I can read them wherever I am by bringing them up on my smart phone! You are also able to download Adobe PDF documents of the books from archive.org. It's a small link on the left hand side of the page when viewing the book. There are links for other documents also: color pdf, black and white pdf, EPUB, Kindle and others. The plain text is typically an OCR (optical character recognition) version. Many of the letters do not translate well from a scanned image to text. For this reason, the text version is typically not very helpful.
Here are a few of the books for my ancestor locations:
Bixenman family - Lake County Indiana - https://archive.org/details/standardhistoryo01howa
Bixenman family - Howard and Chariton Counties, Missouri - https://archive.org/details/historyofhowardc01nati
Doran and Kelly families - Hancock County, Illinois - https://archive.org/details/historyofhancock00greg
Panther family - Des Moines County, Iowa - https://archive.org/details/historyofdesmoin00wes
Menke, Kempker, Harmeyer families - Lee County, Iowa - https://archive.org/details/historyofleecoun00west
I encourage you to at least take a look through the history book of each of the counties in which your ancestors lived. You may be surprised at the information you discover!