How prevalent was lynching in the 19th century as compared to the early 20th century?
Lynching was to some degree more prevalent in the late 1800s than it was in the early 1900s. There are, however, a few aspects of this that require some attention.
First, the raw numbers say that lynching was more common in the late 1800s than in the early 1900s. But this is much more true if we include lynchings of both white people and black people. Using this link, we can see that there were an average of something like 152 lynchings per year between 1882 and 1900. In the 18 years after 1900, the average fell to something around 75. We must note, however, that if we look only at lynchings of African Americans, there is much less of a drop. In the years before 1900, the average number of African Americans lynched was about 75. That dropped after 1900, but only to about 68 per year. In short, there was not nearly such a significant drop in lynchings of African Americans after the turn of the century.
A second thing that needs to be mentioned is that the 1890s were a time in which lynching was much more common than in other years. In the period beginning in 1891 and ending in 1901, about 112 African Americans were lynched each year. This is, of course, much higher than the numbers for the years before or after.
It is safe to say, then, that the 1890s were the peak period of anti-black lynchings. The late 1800s in general saw more lynchings than the early 1900s. Lynching declined after the turn of the century, though the decline was more significant with regard to lynchings of whites than of blacks.