US IRS Tax Assessment Lists at Ancestry.com
To make effective use of this database, one has to use the guides to learn the district number for the desired part of the state one needs. This can be found using the microfilm guide compiled by NARA for the state in question. Searchers cannot simply search based by county.
I wrote an article on using the lists a year ago for the Ancestry.com blog: http://blogs.ancestry.com/circle/?p=2760
It needs updating for those individuals whose names are not unusual and are city dwellers. I'm trying to use the database to find some Watsons in Pennsylvania and there are several. When I've had time to sit down and work it out, we'll blog about it.
One thing about the title here that is somewhat misleading, the majority of thse records are in the 1860s. The VAST majority. The title says 1862-1918, but don't let that lead you astray.