Electric currents in the cusp region are reviewed from viewpoints of history and energy conversion. During late 1980s and early 1990s, there were debates on the cause of the cusp region current system (cusp Region 0 field‐aligned current [FAC] and cusp Region 1 FAC, and relevant ionospheric current). The major debates were whether the cusp part Region 1 FAC is an extension of the non‐cusp‐part dayside Region 1 FAC or whether they are generated in different regions independently. The independency of the cusp current system, which was demonstrated by many observations, suggests additional extraction of energy from the magnetosheath‐like flow (e.g., deceleration) inside the polar magnetosphere. An extra deceleration is theoretically possible by adding a substantial local obstacle such as the outflowing ionospheric ions through the mass‐loading effect, which conserves momentum but not kinetic energy. Thus, two different dynamo (J · E < 0) mechanisms most likely exist between the dayside Region 1 and 2 FACs and cusp Region 1 and 0 FACs, forming “double openness,” which was introduced by Vasyliunas [1995]. The other debates (e.g., roles of mesoscale FACs, mapping to high latitude, and current carriers problems) are also reviewed in the light of new observational knowledge after Cluster.