James Parkinson was born in Shoreditch, London, England. He was the son of John Parkinson, an apothecary and surgeon practising in Hoxton Square in London. In 1784 Parkinson was approved by the City of London Corporation as a surgeon. He never became a physician, as many mistakenly call him.
On 21 May 1783, he married Mary Dale, with whom he subsequently had six children. Soon after he was married, Parkinson succeeded his father in his practice in 1 Hoxton Square. He believed that any worthwhile surgeon should know shorthand, at which he was adept.
In addition to his flourishing medical practice, Parkinson had an avid interest in geology and paleontology, as well as the politics of the day.
Parkinson was a strong advocate for the under-privileged, and an outspoken critic of the Pitt-government. His early career was marred by his being involved in a variety of social and revolutionary causes, and some historians think it most likely that he was a strong proponent for the French Revolution. He published nearly twenty political pamphlets in the post-French Revolution period, while Britain was in political chaos. Writing under his own name and his pseudonym "Old Hubert", he called for radical social reforms.
Parkinson called for representation of the people in the House of Commons, the institution of annual parliaments, and universal suffrage. He was a member of several secret political societies, including the London Corresponding Society. In 1794 his membership in the organization led to his being examined under oath before William Pitt and the Privy Council to give evidence about a trumped-up plot to assassinate King George III. He refused to testify regarding his part in the popgun plot, until he was certain he would not be forced to incriminate himself. The plan was to use a poisoned dart fired from a pop-gun to bring the king's reign to a premature conclusion. No charges were ever brought against Parkinson but several of his friends languished in prison for many months before being acquitted.
Parkinson turned away from his tumultuous political career, and between 1799 and 1807 published a number of medical works, including a work on gout in 1805. He was also responsible for the earliest writings on the subject of peritonitis in English medical literature.
Parkinson was the first person to systematically describe six individuals with symptoms of the disease that bears his name. He did not formally examine these patients but observed them on daily walks, and in some cases obtained from them their disease-symptom histories by simple inquiry. It was Jean Martin Charcot who coined the term "Parkinson's disease" over 60 years later.