Short answers, pulled from the story.
Simon Cameron was a Pennsylvania businessman and politician who served four terms as a United States senator and as Secretary of War under President Abraham Lincoln at the start of the Civil War. He built one of the most durable political machines in American history, which dominated Pennsylvania Republican politics until the 1920s.
Cameron was dismissed by Lincoln on the 11th of January 1862, following the scandal over a paragraph Cameron inserted in his annual departmental report calling for freed slaves to be used to suppress the Confederate rebellion. Lincoln, believing the decision to emancipate was his alone, had the paragraph removed and replaced Cameron with Edwin M. Stanton.
Cameron arrived in Chicago as Pennsylvania's favorite son candidate for the presidential nomination. On the first ballot, Pennsylvania cast 47 of its 54 votes for him; by the third ballot, 52 of those votes shifted to Abraham Lincoln, who won the nomination. Lincoln's manager David Davis made commitments, later disputed, to bring Cameron into the cabinet in exchange for Pennsylvania's support.
In August 1838, Cameron served as one of two commissioners adjudicating traders' claims under a treaty with the Winnebago Indians at Prairie du Chien in Wisconsin Territory. Allegations of corruption arose, and Cameron's biographer Erwin S. Bradley concluded he exceeded his instructions, though the charges were never proved. The episode earned him the mocking nickname the "Great Winnebago Chief."
On the 12th of March 1877, Cameron sent his resignation to Governor Hartranft by special messenger. That same night, he summoned every Republican member of the Pennsylvania legislature to his mansion and asked each to sign an endorsement of his son James Donald Cameron for the Senate seat. The Republican caucus voted for Don Cameron the following day with only one dissent.
The Cameron machine dominated Pennsylvania Republican politics from the 1860s until the 1920s, outlasting Simon Cameron by several decades. Control passed from Simon Cameron to his son Don Cameron, then to Matthew Quay, and then to Senator Boies Penrose.