lenox was born in kirkcudbright, scotland and emigrated to philadelphia sometime before the outbreak of the revolutionary war. when war broke out, he joined the continental army and was commissioned captain of the 3rd battalion of the pennsylvania militia. while fighting the hessians at fort washington in 1776, he was wounded, taken prisoner, and held by the british for eighteen months. following his release, he served as aide-de-camp with the rank of major to major general anthony wayne. lenox also joined philadelphia's first city troop. while a member, he led a successful rescue of james wilson, one of the "founding fathers" of the united states and a signatory of the declaration of independence, when wilson and others barricaded themselves in wilson's home ("fort wilson") during a riot in response to wilson's successful defense of 23 people from property seizure and exile by the state government.