Palmer amaranth (Amaranthus palmeri S. Watson) is one of the most troublesome weeds in North America due to its rapid growth rate, substantial seed production, competitiveness, and the evolution of herbicide resistant populations. Though frequently encountered in the South, Midwest, and mid-Atlantic regions of the US, Palmer amaranth (AMAPA) was recently identified in soybean fields in Genesee, Orange, and Steuben counties, NY, where glyphosate was the primary herbicide for in-crop weed control. This research, conducted in 2022 and 2023, aimed to 1) describe the dose response of three putative resistant NY AMAPA populations to glyphosate, 2) determine their mechanisms of resistance, and 3) assess their sensitivity to other postemergence (POST) herbicides commonly used in NY crop production systems. Based on the effective dose necessary to reduce aboveground biomass by 50% (ED50), the NY AMAPA populations were 42- to 67-times more resistant to glyphosate compared to a glyphosate-susceptible (GS) population. Additionally, the NY populations had elevated 5-enol-pyruvylshikimate-3-phosphate synthase (EPSPS) gene copy numbers located within extrachromosomal circular DNA (eccDNA), ranging from 25 to 135. NY populations were also poorly controlled by labeled rates of the Weed Science Society of America (WSSA) Group 2 herbicides. Some variability was observed among the populations in response to WSSA Group 5 and 27 herbicides. All populations were effectively controlled by labelled rates of herbicides belonging to WSSA Groups 4, 7, 10, 14, and 22. Additionally, a preliminary study was conducted to assess the impact of temperature on AMAPA’s early growth and sensitivity to glyphosate based on glyphosate-resistance (GR) status. Temperature did not affect the early growth of the GR NY population; however, elevated temperatures reduced the biomass of the GS Nebraska population. The dose of glyphosate required to reduce the aboveground biomass of the GR population by 50% ranged from 451 to 1,170 g ae ha-1 depending on chamber temperature. The ED50 value of the medium-temperature treatment was significantly lower than that of the high-temperature treatment; however, no other contrasts were statistically different. This result is suspected to be spurious due to the lack of a biological explanation. Additional research is warranted to confirm whether NY AMAPA populations have evolved resistance to the tested herbicide SOAs, to further investigate the impact of temperature on glyphosate sensitivity, and to develop effective AMAPA management strategies suitable for NY crop production.