Original landrace maize varieties have been replaced by modern open pollinated varieties (OPVs) and hybrids in many places, but the elite materials were formed using landraces as parents.  Landraces may have been successful parents, passing on many alleles to the OPVs and inbreds; they may have been poor parents, appearing in the pedigree but contributing few useful alleles following selection; or they may not have been used as parents at all.  Knowing which landraces belong to each category can make future breeding efforts more efficient, and guide the search for new useful alleles.  Inbred lines created by CIMMYT have played an important role in hybrid maize production in developing countries.  These inbreds (called CMLs) were mainly extracted from OPVs that were themselves created by mixing many different landraces from around the world. 209 CMLs were analysed with 22 individuals from each of 23 landraces, representative of almost all 25 major landraces from Mexico.  Many were important in the formation of the CMLs.  These were analyzed with SSRs to see the contribution of each landrace to the CMLs using Structure to assign individuals to their known population, but allowing the CMLs to vary.  Results indicate that many of the CMLs contain variation from multiple landraces, many not represented in this study, (in agreement with their pedigrees).  However, many looked like only one of the landraces,  indicating considerably less mixing in the CIMMYT populations since their formation than expected.  Landraces that were used often to form breeding populations were found to be the most similar to the highest number of CMLs.  However, there were also some cases of landraces that had been used often as parents whose variation are not reflected in any of the CMLs.  These may have been poor parents, and had their variation selected out over subsequent generations.