The U.S. cotton (Gossypium spp.) industry has shifted from a mandated, vertically integrated national industry to a global industry with most raw cotton exported for spinning and weaving. This new focus necessitates continued development of upland cotton, G. hirsutum L., with superior fiber properties to maintain U.S. competitiveness. TAM 06WE-621 (Reg. No. GP-979, PI 671964) was developed to provide parental material with improved fiber properties that produces improved yarn. Fiber and yarn properties of this line were compared with two cultivars, 'FM 832LL' and 'DP 491', when grown at Weslaco, TX, during 2009 and 2010, and compared with five cultivars in the Regional Breeders Testing Network (RBTN) trials of 2012. TAM 06WE-621 produced stronger fibers than either control at Weslaco in 2009 and 2010 and stronger fibers than five control cultivars in the 2012 RBTN. Fiber length of TAM 06WE-621 was longer than the controls at Weslaco in 2009 and equal to the controls in 2010, and it averaged longer upper half mean length than four of the five 2012 RBTN control cultivars. This new germplasm line produced 50 count (50 Ne) mini-spun carded yarn 35 and 18% stronger than the strongest control in 2009 and 2010, respectively, and required 49 and 19% more work to break, respectively. TAM 06WE-621 was yield competitive in central and south Texas and exhibited more and larger seeds per boll.