  We observe a localized cnoidal (LCn) state in an electric circuit network.
Its formation derives from the interplay of non-linearity and the topology
inherent to a Su-Schrieffer-Heeger (SSH) chain of inductors. Varicap diodes act
as voltage-dependent capacitors, and create a non-linear on-site potential. For
a sinusoidal voltage excitation around midgap frequency, we show that the
voltage response in the non-linear SSH circuit follows the Korteweg-de Vries
equation. The topological SSH boundary state which relates to a midgap
impedance peak in the linearized limit is distorted into the LCn state in the
non-linear regime, where the cnoidal eccentricity decreases from edge to bulk.
