The recent seismicity of the Blida region could not be assessed without due consideration to its earthquake history. We reexamine the 1867 Mouzaïa–El Affroun earthquake, which is one of the largest historical earthquakes that occurred in the region, and use the earthquake history of the last 250 yrs to help decipher the complexity of the active deformation of the Mitidja basin (MB). Newly discovered contemporary accounts are used to assess and discuss the extent and intensity of events considered of particular interest and which occurred before the installation of the Algerian seismic network. The 78 significant earthquakes tabulated with comments, among which are 27 events that were not reported in any previous work or catalog, make it clear that the southern border of the MB has long been markedly more active than the northern border. A main objective of this article is to make available the historical data that can be used in further investigations.