Tracing the family tree back can get very frustrating at times. Going back before 1850, the data gets sparse and erratic. One thing that makes it difficult is that prior to 1850, the US Census only recorded the names of the head of household - and in 1790 and 1800 even the full first name was often not recorded as they would use first initial only. To make matter worse, in the newly forming states births and deaths were not recorded. Some of the counties where my family lived did not start recording births and deaths until the 1870s. Scattered and erratic data.
Also, the data within the US Census itself can often be incorrect. Take for example my Great Great Grandmother Elizabeth (Thacker) Barker's family. In 1850, she was 10 years old and I found her family record pretty easily. But look how things had changed in the 1860 census. Ages and birthplaces didn't quite align.
Going from 1860 to 1870 was just as bad. Ages and birthplaces were askew again, as were a few of the names.
Moral of the story: take the information found online with a little bit of leeway. The information might be slightly off. Which makes work discovering your family tree even more difficult.
The US population was exploding. It was already 2 to 3 million in the late 1700s and had grown to 23 million by the mid 1800s!