This chapter examines the unprecedented transformation of the Board of Trade from a small advisory body of seventeen staff in 1786 overseeing colonies and trade with them, into very large and ramified executive office of state with many internal departments and satellite registration agencies with 7500 directly employed staff, engaged in micro-economic regulation of the domestic economy. The Board became a central underpinning structure for the system of British economic governance. The chapter first reviews the key stages between 1764 and 1815 which reoriented the Board, before presenting its vast range of functions acquired by 1914. The result was a regulated, not a laissez faire economy, although many external tariffs were eliminated and much regulation was for market-enabling. However, the Board did not achieve integration in its overarching regulatory policy-making capability. The chapter shows that mainstream theories of state development (war, tax, ideas, slavery, empire, particular parties, open access institutions, borrowing from others, interest group lobbying and capture, and bureau-shaping) do not explain transformation, and therefore it is valuable to examine endogenous processes. The chapter concludes with a brief overview of twentieth-century developments.