Maize is the most diverse crop plant analyzed at both morphological and molecular levels (Anderson and Cutler 1942; Brown 1949, 1985; Buckler et al. 2006; Duvick 1981; Galinat 1961; Goodman 1968; Ho et al. 2005; Iltis 1972; Timothy and Goodman 1979; Vigouroux et al. 2005; Xia et al. 2005). Enormous levels of allelic polymorphism exist in maize (Chin et al. 1996; Guo et al. 2004; Goodman and Stuber 1983; Stuber et al. 1980) and this diversity has allowed for selection of beneficial agronomic traits that have been utilized in breeding over the millennia (Dudley 1988; Pollak 2003; Vigouroux et al. 2002; Yamasaki et al. 2005). Visible phenotypic trait diversity due to natural allelic variation or induced mutation has allowed a greater understanding of maize biology, which can also lead to agronomic improvements (Coe 2001; Peterson and Bianchi 1999; Rhoades 1984; Sachs 2005). Maize germplasm stock centers exist to categorize, preserve, maintain, and distribute this genetic diversity to researchers, breeders, educators, and others who can utilize this variation (De Vincente 2004; Dillmann et al. 1997; Hoisington et al. 1999; Troyer 1990). These genetic resources in maize have proven to be extremely useful and germplasm centers will ensure that they continue to be so. Maize genetic resources are divided into two major categories: (1) genetic stocks and (2) germplasm accessions (Bird 1982; Bretting and Widrlechner 1995; Bretting and Widrlechner 1995; Brown and Goodman 1977; Crossa et al. 1994; Goodman 1990; Janick 1989; Scholl et al. 2003; Shands 1990, 1995; Shands et al. 1989; Taba et al. 2004; White et al. 1989; Wilson et al. 1985). The Maize Genetics Cooperation Stock Center (MGCSC) specializes in maize genetic stocks. Other types of maize and wild Zea germplasm are maintained and distributed by the North Central Regional Plant Introduction Station (NCRPIS) in Ames, Iowa. Maize germplasm can also be obtained from Centro Internacional de Mejoramiento de Maiz y Trigo (CIMMYT) in Mexico. CIMMYT specializes in tropical germplasm. The stocks of all three collections are backed up at the National Center for Genetic Resources Preservation (NCGRP) in Fort Collins, Colorado.