[4] Hosack was born in New York City, the first of seven children of Alexander Hossack [sic], a merchant from Elgin in Scotland, and his wife Jane Arden.

While Hosack was studying at New York Hospital in April 1788, a violent crowd formed outside to protest body snatching, the practice of illicitly obtaining cadavers from graveyards for use in medical training.

The rioters had gathered after a medical student taunted a group of children by waving a corpse's arm at them from a window, resulting in several days of violence that was later called the doctors' riot.

[2] In 1789, after graduating from Princeton, Hosack enrolled as a medical student under Dr. Nicholas Romayne, where he regularly visited homes for the poor and insane, as they were among the few places to offer clinical instruction.

Upon arriving in the United Kingdom, Hosack matriculated at the University of Edinburgh, where he was reportedly horrified to find his knowledge of botany was sorely lacking.

Well received by some of the leading scientific minds of the period, Hosack spent much of his time in their botanical gardens and lecture halls.

[8] Three years after the duel, Burr was tried and acquitted on a charge of treason for a conspiracy to form a new nation in the Louisiana Territory and Spanish Texas.

[8] One of Hosack's most distinguished students was a celebrated New York City physician, John Franklin Gray, who later became the first practitioner of homeopathy in the United States.

[9][10][11] In 1798, following a yellow fever epidemic, Hosack proposed opening the first lying-in hospital in New York, a maternity clinic where he could offer health care to poor pregnant women.

[12] He raised funds from subscribers, including Alexander Hamilton, to purchase a house on Cedar Street where the Lying-In Hospital opened in 1799.

[8] It was the first public botanical garden in the United States,[18] established with his purchase of twenty acres of rural land on the outskirts of New York City for just under $5,000,[19] equivalent to $112,000 in 2023 dollars.

By 1805, after Hosack had spent $75,000 on the effort, the garden was home to 1,500 species of plants from all over the world, including some rare specimens contributed by Thomas Jefferson.

[22] Hosack's funds were insufficient to support such a project indefinitely, and it was suggested that he was so preoccupied with his endeavors in the creation of Rutgers Medical College that he had neither time nor money to continue the garden.

[1]: 55 Early in 1791, shortly before receiving his medical degree, Hosack married Catharine Warner, whom he had met while studying at Princeton.

These personal tragedies, along with epidemics of yellow fever that hit Philadelphia in 1793 and New York in 1795 and 1798, led Hosack to devote much of his life thereafter towards the expansion of medical knowledge and education, as well as the training of doctors in caring for women and children.