The Orion OB1 association as studied by the CVSO. The most prominent and well-known stellar groups and nebulosity found across this extended region are labeled. Throughout this work, we assume the OB1b subassociation to be the area contained within the dashed-line circle roughly centered on ϵ Ori, as defined in Briceño et al. (2005). The OB1a subassociation is all the area west of the straight dashed lines and of OB1b. The B Cloud is considered here as the region east of the boundary with OB1a and OB1b, north of −2°, while the A Cloud is roughly the region east of 5^h28^m, south of −2°, and excluding OB1b (optical image courtesy of Rogelio Bernal Andreo, DeepSkyColors.com).