I have just noticed that there are 5 counties missing in the 1860 full count data:
- Hernando, Florida: stateicp=43 and countyicp=530
- Bienville, Louisiana: stateicp=45 and countyicp=130
- Hancock, Mississippi: stateicp=46 and countyicp=450
- Sunflower, Mississippi: stateicp=46 and countyicp=1330
- Washington, Mississippi: stateicp=46 and countyicp=1510
I have been able to locate county aggregates for these counties in the ICPSR data by Haines et al., so these counties definitely had census data collected in 1860. Is it possible that their codes have been mis-identified in the IPUMS 1860 full count data?