Ancestry.com, continuing their programme of digitising government records (they have a deal in place with the UK's Public Records Office for Census data) have digitised US tax records from 1862 to 1918.
Want to know what Abraham Lincoln paid in 1864? $1,296 in tax from a salary of $25,000 - or something over $1/2 million in today's money.
You can also see that Andrew Carnegie earned $12 million (or $84,000 in 1865). If you're looking for Mark Twain, remember his real name was Samuel Clemens.
The list of other data items they have compiled is enormous - this is just a short section from the list.
Sourced from BusinesWeek.