Kilbeggan was incorporated by a 1612/3 charter of 10 James I. Its corporation comprised a portreeve, 12 burgesses, two serjeants-at-mace, a recorder, a town clerk and a seneschal. Its history as related in 1790 was that:
At the Restoration, the then Earl of Cavan wrested this Borough from various contending Roman Catholics and it remains at this day under the absolute influence of Mr Lambart, descended from a younger Branch of the Earl's family. This gentleman having been, for some time, a constant absentee, it is generally brought to market and proves a sure resource for those pests of the community, parliamentary adventurers.421
The Lambart family represented the borough themselves for most of the century, with a break between 1783 and 1797 which, it was said, was caused by a dishonest clerk who had embezzled a large sum of money which obliged Charles Lambart (1192) to sell both seats in 1783; his heir, Gustavus Lambart (1194), was a minor in 1790. Kilbeggan was a village of 500-600 inhabitants. It was 'a close Borough, whose sole electors are the twelve Burgesses and a very few Freemen appointed to save appearances, not to encourage independence'.422 It was disfranchised at the Act of Union; the £15,000 compensation was paid to Gustavus Lambart.