[2] He read law in the office of his uncle, Judge Briscoe G. Baldwin, to become a lawyer and was admitted to the bar by age 19.

[9][10][11] Gainesville was in Sumter County, which had a sizeable and growing population profiting from a booming economy and from enslaved labor farming the rich soil; the people Baldwin associated with were "men of the first rank in the legal profession, of high attainments in scholarship, of genuine literary taste and culture, and of fun-loving spirits and mirth-provoking propensities"—these were the "flush times" he would describe in his first book.

[13] In August 1849, he was defeated by Democrat Samuel Williams Inge in a bid for the United States Congress by only 400 votes.

[17][18][19][20] Chief Justice Stephen Johnson Field praised Baldwin's opinion in Hart v. Burnett (1860),[21] concerning pueblo land grants, as a model of scholarly learning.

[28][29] In 1863, during the American Civil War, another son, Joseph G. Baldwin, Jr., was accused of plotting with a group of sympathizers with the Confederate States of America to capture military posts in California.

[31] Their daughter, Kate S. Baldwin, married John B. Felton, who was her father's law partner and later mayor of Oakland.