Over the last 50 years significant advancements have been made in the southern yellow pine (SYP) forests in the U.S. south. Due to silvicultural changes and large scale reforestation efforts the US south has seen significant increases in standing volume (more than 120% over the period). Landowners that grow SYP plantations largely manage for trees that are harvested to produce dimensional lumber. With the changes in growth patterns it is of interest if there have been any changes in structural properties of the lumber that is produced from timber grown today. Landowners desire confirmation that what they are doing in terms of management is maintaining the quality and strength of lumber that the market demands. This information is critical because timberland owners’ plant and manage trees that will ultimately be brought to market at lumber 25-40 years into the future. In an effort to provide clarity to this topic this dissertation investigates: 1) The extent to which the specific gravity (SG), bending strength (modulus of rupture, MOR), and bending stiffness (modulus of elasticity, MOE) of small clear specimens of SYP have changed, particularly with respect to reduction(s), during the interval from approximately 1965 to 2015. 2) The extent to which the compression parallel to grain and perpendicular to grain strength of small clear specimens of SYP have changed, particularly with respect to reduction(s), during the interval from approximately 1965 to 2015. Use statistical analysis of variance to investigate potential differences among data from a historical 1966 data set, a 2014 in-grade data set, and a 2018 staircase material data set. 3) The nature of the relationship between and among SG, MOE, and MOR of small clear specimens of SYP and how these relationships may have changed, during the interval from approximately 1965 to 2015. Use statistical regression analysis to explore changes to the interrelationships of SG, MOE, and MOR among the three samples, with particular interest toward how these may impact or influence non-destructive evaluation. This work consists of 3 independent chapters using varying appropriate statistical methods and is accompanied by an introduction and conclusion.