We present a detailed analysis of the 10 June 2019 4.0 Ohio earthquake sequence, which is the largest earthquake that struck Lake County, northeastern Ohio, since 1986. This sequence is well recorded by local seismic networks, which provides an unprecedented opportunity to understand the local seismotectonics. We utilize a waveform‐based cross‐correlation method to identify times more events than reported by the Advanced National Seismic System (ANSS) Comprehensive Earthquake Catalog: the whole sequence started with several small earthquakes ( 1–2) beginning 12 March 2019, and the last one occurred immediately before the 4.0 mainshock; many previously unreported aftershocks ( 0.3–2.2) are found, which were active for the first week after the mainshock; another major sequence with a 7 December 2019 2.6 mainshock occurred and also started with a few smaller events beginning in mid‐November and was followed by its own aftershocks. The relocated seismicity delineates a linear feature, orientation of which is consistent with the resolved focal plane that may correspond to the ruptured fault. Our results highlight that closer monitoring of local seismicity is crucial for understanding the seismotectonics and mitigating future seismic hazard around the southern Great Lakes.