Then there are the state-run agencies and groups which correlate their county genealogical societies. They are often greater funded than county groups and publish a more professional grade of publication. You can use "State Genealogical Publications" as a search phrase on your search engine and you will get each separate state web site which offers genealogical information. Find the state that you are interested in and click the link. Or you can sort through a particular state's long list of agencies until you find their history or genealogical section.
But by far, county-run genealogical organizations which sort through local data and publish marriages, cemeteries, probate lists, obituaries, local directories and other direct sources are going to be your bread and butter when it comes to finding family information. Around the turn of the 20th century many counties compiled articles concerning separate counties. These rather thick books had valuable early settler information. Some have copied such efforts with a centennial publication with more recent additions. County-run organizations are the grass root groups that are lead by local volunteers. They have often replaced the need to visit a local church or courthouse for information. Yet, there is a vast difference between one county web site and another. There are a couple ways to sort through the thousands of counties across the nation. You can always type the particular county's name and the state it resides in on your search engine, like "Polk County, IA." You will see amongst the list, municipal as well as local business web sites and other local identities listed. Among these you can sort out the county genealogical sites, libraries, local history groups, and the area chapter from the USGenWeb project.
The USGenWeb project is a group of volunteers working together to provide free genealogy web sites for genealogical research in every county and every state of the United States. Hosting a web site can be costly, not to mention you need someone with web site understanding to manage them. Thus the USGenWeb project full fill a vital roll. They do not have all the information of a local area as they do rely on volunteers to submit information, but they are a good source to begin with. Most often these web sites have a link to various local publications which is the culmination of local research on documents and places.
Local county genealogical societies and groups provide a wide range of services which can directly fit into your research. One important feature is the "look-up" volunteers who have access to various genealogical and courthouse records and publications. I am often amazed at how these volunteers have vast stores of genealogical information about counties and places which are hundreds of miles from where they live. They live in one state and have in their possession books about another state and county. You may be surprised where you will end up in locating data about your family.
Lastly, books are a good source of history for various locations in the United States. But, finding what you want about your particular family history may require some downtime in front of the fireplace. Many times the history of migrations or early settler life can also aid the research in hints as to where to look for more information as well as explain why more information is not available, like the courthouse burned down or a flood wiped out a cemetery.
As time advances, good hearted souls find more dusty documents in basements and bring them to light in new publications. Time may be the barrier to discovering your family's heritage, but time may also allow such information to eventually make it's way to you.