For IPUMS. Where can I find the names of all slave holders in 1860 and the number of slaves they owned?
The IPUMS-USA Slave PUMS project has five samples (two from 1850 and three from 1860), but none of these contain all of the slave records for their respective years and, therefore, they cannot claim to contain every slave holder either. If you are interested in a specific county from one of the states represented in the 1860 complete count sample, you may be able to find all of the names of slave holders in that county (using the variables SH1LN, SH1FN, SH2LN, and SH2FN), but it is important to understand that these data files contain records for slaves and not slave holders. To gain a better understanding of these samples, I recommend reading the About page and User’s Guide.
You may also try searching other sources such as Ancestry.com or the US Gen Census Project, which is a volunteer driven transcription project that includes transcribe slave schedules that may contain the information you are looking for. Their records are organized by state and county, but they do include labels to indicate slave records. I hope this helps.