Solid-liquid interfaces provide a catalytic environment for many important chemical and physical processes. The catalytic potency of these environments stems largely from their tendency to produce strong, persistent electric fields. These fields push and pull on ions, electrons, protons, and molecules to help them find transition states and overcome activation barriers. Over a century of scientific effort has been aimed at understanding the properties of these fields, how they can be controlled, and how they can be leveraged to enable advances in the chemical sciences. However, despite this effort, surprisingly little is known about the structure of the electric field profiles at these interfaces.