Where would I find statistics on occupation as a percentage of US workforce over time?

I’m trying to graph how many farmers there have been, over time, as a percentage of the US workforce. A similar example is here (the parts in brown), but I can’t seem to find the numbers from a primary source. I tried the Bureau of Labor Statistics, but not having much luck – for some reason they say they exclude most agricultural statistics. And the National Agricultural Statistics Service only provides data stretching back to 1910 or so.

Are there any other sources I’m missing? This shouldn’t be so hard to find…