A: London, England, United Kingdom
In 1865 James Clerk Maxwell published "A Dynamical Theory of the Electro-Magnetic Field" in the Transactions of the Royal Society of London. In this culminating paper on the foundations of electromagnetic theory Maxwell developed twenty field equations of electromagnetism, clinching the theory that light was a form of electricity.
Maxwell had already found in 1862 a link of a purely phenomenological kind between electromagnetic quantities and the velocity of light, but this 1865 paper provided a new theoretical framework for the subject, based on experiment and a few general dynamical principles, from which the propagation of electromagnetic waves through space followed without special assumptions about molecular vortices or forces between electrical particles. The paper provided a theoretical framework, based on experiment and a few general dynamical principles, for the propagation of electromagnetic waves through space.