Early life factors play important roles in disease susceptibility in later life. However, the relationship between dietary factors in early life on childhood growth, especially linear growth, remains unclear. This research aimed to improve our understanding of the associations between dietary factors in early life (i.e., infant feeding practices and age of introduction of solid foods) and childhood growth, especially using ulnar length as a surrogate measure of length/height, in a cross-sectional study of 1634 mother-child dyads across eight study centers in the National Children's Study Formative Research in Anthropometry in the United States from 2011-2012 (Chapter 1). Chapter 2 described the data acquisition and preprocessing procedures used in this research and provide practical guidelines of data quality control. In Chapter 3, predictive models for exclusive breastfeeding (XBR) initiation and duration was developed. Discriminant analysis revealed maternal sociodemographic factors had greater discriminating abilities to predict XBR initiation and XBR for 6 months, compared to child birth characteristics and maternal perinatal factors. Chapter 4 demonstrated that ulnar length can serve as an accurate and reliable surrogate measure of recumbent length in healthy infants/children aged 0-1.9 years and of height in healthy children aged 2-5.9 years, respectively. Bland-Altman plots and mixed-effects linear regression analyses showed that the three simple and portable tools (i.e., caliper, ruler, and grid) used to measure ulnar length could be used interchangeably in terms of prediction accuracy. Chapter 5 focused on assessing the interplay among gestational weight gain (GWG), birthweight, infant feeding practices, and childhood anthropometrics. Longer duration of breastfeeding reduced the positive associations of GWG and birthweight with weight-for-age z-scores, weight-for-height/length z-scores, and body mass index-for age z-scores in non-Hispanic Whites. These findings underscore the importance of promoting breastfeeding among women with excessive GWG to mitigate childhood obesity. Longer breastfeeding and a later age at introduction of solid foods had positive effects on ulnar length, a linear growth parameter of upper extremity, in Hispanics. Future prospective research aiming to investigate the underlying mechanisms that drive ethnic variation in these associations between early life dietary factors and childhood growth is warranted (Chapter 6). / text