The NDSU EarlyGEM or the Early Germplasm Enhancement of Maize (Zea maize L.) is a long term incorporation program designed to increase the genetic diversity of short season hybrids. Starting in 1999, exotic GEM breeding crosses derived from temperate accessions: BR52051, CH05015; tropical accessions: SCR01, CUBA17, FS8B; and tropical hybrid DKB844 along with late checks: B73, Mo17, and Iowa Stiff Stalk Synthetic (BSSS), were adapted to short-seasons and incorporated via a modified backcross (BC) procedure. This study was designed to assess the genetic diversity in exotic derived BC1:S1 lines and their competitive potential as sources of new and unique hybrids. Useful genetic diversity was evaluated with testers belonging to opposite heterotic groups, LH176 representing a non stiff stalk and TR3026 x TR2040 a stiff stalk testers and were tested in five North Dakota environments over two years (2009 and 2010). All the traits showed highly significant (P<0.01) differences across genotypes except root and stalk lodging. Among 236 experimental testcrosses, 64 were statistically not different (LSD, 0.05) to industry hybrids for grain yield. BC derived lines from BR52051, CHO5015, DKB844 showed diverse alleles for low grain moisture (below 87 relative maturity days) at harvest and high grain yield. SCR01, BR52051, CHO5015 and CUBA117 derived lines produced hybrids with high grain oil (4. 9% vs. 4.1%) and grain protein (10.4% vs. 9.1%) contents compared to top checks. The results showed that the exotic incorporations are the sources of unique new alleles for early maturing maize not present in existing US germplasms (e.g. B73, Mo17, and BSSS). Even though each exotic cross was unique to integrate diverse alleles, utilizing multiple unique exotic crosses for incorporation showed large variation for specific traits. Phenotypic correlations of traits showed grain moisture played the most important role for short season hybrid development. Exotic incorporation through NDSU EarlyGEM has shown a new way of breeding early maturing maize keeping the breeding program open and genetic diversity high.