Since Liouville provided the first examples of transcendental numbers in 1844 the discipline has evolved from the study of particular numbers, to values of the exponential function, to values of other functions, then to the algebraic independence of numbers associated with elliptic curves, commutative algebraic groups, and Drinfeld modules and t-modules. In this lecture we will trace this evolution, paying particular attention to the infusion of new ideas into the discipline and to how extensions of these ideas lead to relatively recent results.