John Brown married Margaretta Mason in 1799 in New York City. Brown likely met Margaretta through mutual friends, John and Maria Beckley. John was 42 years old and Margaretta was 26 when they married. Soon after their marriage, they had their first son, Mason (1799-1867). In 1801, the family moved into Liberty Hall. John was still a Senator and was frequently in Washington but letters between Margaretta and John show their deep affection for each other.
In 1802, Margaretta wrote to John, Life is too short and too barren in happiness, to admit of such great deductions from the few joys it can boast; and conjugal felicity such as ours, is too rare, and too valuable to be sacrificed to anything but imperious necessity. It is my most earnest desire my love, that you may find our separation as painful as I do…Private Collection.
In 1801, their second son Orlando was born. They had three more children, none of whom survived into adulthood: Alfred (1803-1804), Alfred (1804-1804), and Euphemia (1807-1814).