Pinkerton could trace his line to seventeenth-century Gorbals, a Scottish burgh on the south bank of the River Clyde, annexed by Glasgow in 1661, which by the nineteenth century had become a bustling factory and workshop center for more than 35,000 people living in squalid thatched houses and multistory tenements along narrow streets.
William Pinkerton was a grim-faced muscular man, with a gloomy personality and a modest amount of schooling, who stood about six feet tall and was "straight built," according to his son Allan. He likely supplemented his falling income as a home handloom weaver by serving as a Glasgow city jail trustee, which gave him some standing in the community. Allan Pinkerton, who was prone to fabricating parts of his biography, claimed that his father died as a police sergeant battling rioters, but that story appears to have no basis in fact. William's first marriage was to Isabella Stevenson, who bore him seven children (five of whom lived beyond childhood) and who, according to family legend, died after delivering the last one in 1807. In his mid-forties, William married a thirty-three-year-old cotton mill worker named Isabella McQueen, who had Allan and another son, Robert, who survived to adulthood. Allan was born in 1819 in the couple's third-floor tenement apartment on Muirhead Street. The exact day is in dispute. Biographers have it variously as July 21, August 21, and August 25.
Little can be confirmed about Allan's childhood. Pinkerton's later accounts of it are riddled with inaccuracies. He claimed the household was "completely filled with the tensions of two families existing in a few rooms," but that may not have been the case. William was a stern father, but by the time Allan was five, the children of the first marriage had all left home and only Allan and his brother Robert remained in the apartment. Allan attended elementary school until age nine or ten, when his father died. With a firm grounding by then in reading, writing, and arithmetic he was considered adequately educated for that time. He later regretted not having any more formal schooling and thought he suffered because of it.
After several years of odd jobs for pennies a day, Pinkerton at age twelve decided to apprentice with William McCauley, a Gorbals barrel maker, to learn how to be a cooper. Six years later he had earned a journeyman's card. By then, he was five feet eight inches tall with powerful shoulders and arms from hours spent each day pounding iron barrel hoops with a ten-pound hammer. But he described himself as a "tramp cooper," roaming Scotland and northern England the next four years finding short-term work that ended each time with layoffs.
Industrial unrest swept Glasgow by the end of the 1830s, fueled by a downturn in the British economy, with cotton mill owners cutting wages, thousands of their workers striking, and union leaders being marched off to jail. In 1838, Pinkerton became a Chartist, named for a popular working-class movement whose six-point People's Charter called for democratic reforms and broader suffrage for men. Pinkerton, who became the Glasgow coopers' representative to the Chartist Convention in Birmingham, joined the grassroots revolt because "I was free in name, but a slave in fact," he recalled. He came to worship the frail yet charismatic George Julian Harney, a London communist among the Chartist leaders, and became Harney's strongman as he traveled through Scotland delivering fiery speeches. On November 4, 1839, Pinkerton joined 5,000 men armed with mostly spears and clubs in the Newport, Wales, uprising to free Henry Vincent, an imprisoned Chartist orator. He escaped being among the twenty-two Chartists whom soldiers killed and the sixty-two whom police arrested after scattering the mob with a volley of musket fire.
In April 1841, while organizing a concert at O'Neil's Public House to raise money for striking spinners in Glasgow, Pinkerton couldn't take his eyes off fourteen-year-old Joan Carfrae, a bookbinder's apprentice who was singing soprano in the event. An Edinburgh orphan, Joan had been reared by her aunt, who educated her. She was a kind young girl, who sang in Glasgow's Unitarian Church on Center Street and was as committed as Pinkerton was to workers' rights. Allan courted her for almost a year before they married on March 13, 1842, when Joan was fifteen. She may have misled Pinkerton into believing she was eighteen. He was twenty-two.
The next month, Joan shared a filthy cabin with other women and Allan wedged into the crew's quarters aboard the merchant ship Kent, sailing for America and what the young couple hoped would be a better life. Pinkerton paid for their passage by working as the ship's cooper. Their first stop was to be Montreal, but storms blew the Kent far off course and she foundered 250 miles south on ice and reefs at Sable Island, southeast of Halifax, Nova Scotia. A lifeboat carried them to shore, where Indian raiders promptly robbed them of the few possessions they carried, including Joan's wedding ring. In May, they finally reached Montreal with only twenty-five pennies in Pinkerton's pocket. Allan and Joan found a room in a boardinghouse and Allan scratched out a living in Montreal making beef barrels until he was laid off several months later. Giving up on Canada, the couple planned to book a steamer south to Chicago, but they changed their minds and moved instead to the village of Warsaw, in western Illinois. Calamity struck once more—they were robbed of everything but the clothes on their back—so they decided to return to their original plan and move to Chicago.