Short answers, pulled from the story.
The telegraph by Samuel F. Morse in 1844 changed how money moved across the world and allowed financial crises to ripple between countries within days instead of months. The world economy was more interconnected by the 1850s which made the Panic of 1857 the first worldwide economic crisis.
On the morning of the 24th of August 1857 the president of Ohio Life Insurance and Trust Company announced its New York branch had suspended payments. The company went bankrupt because of fraudulent activities by the company's management and liabilities were said to be $7,000,000 according to an article printed in the New York Daily Times.
The US Supreme Court decided Dred Scott v. Sandford in March 1857 and Chief Justice Roger Taney ruled that Scott was not a citizen because he was black. Kansas land warrants and western railroad securities prices declined slightly just after the decision in early March due to political uncertainty about future territories.
Borough Bank of Liverpool closed doors the 27th of October 1857 while Western Bank of Scotland failed November 9 and City of Glasgow Bank failed two days later on November 11. Government forced to suspend Bank Charter Act 1844 again on November 12 and Bullion in Bank of England started increasing soon after suspension.
Farmers experienced loss in revenue causing banks to foreclose on recently purchased lands which led to financial pressures in Midwestern towns including Keokuk Iowa. Land sales declined dramatically and westward expansion essentially halted until the Panic ended.