Though born the son of a prominent politician, Newton's mother was soon widowed and moved the family to Illinois.

Isaac's widowed mother first moved the family to New Castle, Pennsylvania, shortly after his death, then to Illinois in 1849.

Pearson attended public schools in these two towns and helped to make ends meet by farming, chopping wood, and tending gardens.

[1] By the time the Civil War broke out in 1861, Pearson was working in the office of the clerk of the circuit court.

He lost the position for political reasons in 1864—Pearson was a Republican and the Democrats had just come to power—so then he worked in a banking house in Bushnell, Illinois.

Pearson was elected to the Illinois House of Representatives in 1882 and served a two-year term; he was also named a vice president of the bank.