Length was one of the first two quantities to be specified in the Metre Convention (the other was the kilogram) and has always been at the heart of the Metric System. Indeed the need to make measurements of length has been one of the fundamental requirements of a civilized society.
A description of the evolution of old length (and other) standards can be found in the following article:
A.J. Wallard, "There or thereabouts", Proceedings of the Royal Institution, 1998, 69, 107-122.