That partner was James Fisk.
One man with this first name loaned Pennsylvania $3,000,000 to finance its civil war effort. That man was charged with selling more than a billion dollars' worth of bonds, but his (*)  financial empire collapsed after he failed to complete the Northern Pacific Railroad, thus precipitating the Panic of 1873. Another man with this first name, but not the nickname "Diamond Jim", attempted with his partner to corner the gold market, with disastrous results that caused another panic. That partner was James Fisk. One man with this last name signed an unpopular treaty with Great Britain and was the first Chief Justice of the Supreme Court. For ten points, name this first name of men named Cooke and Gould, and the last name of John, who co-wrote the Federalist Papers.
One man with this first name loaned Pennsylvania $3,000,000 to finance its civil war effort.
Jay