Wire Arc Additive Manufacturing (WAAMWire Arc Additive Manufacturing (WAAM)) is a high-deposition-rate technology poised to revolutionise the production of large-scale metallic components. However, its widespread adoption is hindered by processProcess-induced defects, notably mechanical anisotropyAnisotropy. This study investigates the relationship between microstructureMicrostructure and mechanical propertiesMechanical properties in a large wall structure (200 mm × 80 mm × 9 mm) fabricated from ER70S-6 low-carbon steelSteel using a novel, compact desktop WAAMWire Arc Additive Manufacturing (WAAM) system. The system integrates a 3-axis CNC gantry with a Gas Metal Arc Welding (GMAW) power source. A constant interpass temperatureTemperature of 300 °C was maintained to ensure thermal stability throughout the build processProcess. Microstructural analysis revealed a characteristic anisotropic structure, with large columnar grains oriented along the build direction and distinct layer bands. Tensile testing, conducted in accordance with ASTM E8, confirmed significant mechanical anisotropyAnisotropy. The ultimate tensile strengthStrength (UTS) was found to be 9.1% higher in the longitudinal (deposition) direction (495 MPa) compared to the transverse (build) direction (450 MPa). Conversely, elongation at fractureFracture was greater in the transverse orientation (33% vs. 28%). A uniform microhardness profile along the build height, averaging approximately 221 HV, demonstrated the effectiveness of the thermal management strategy. The results correlate the observed anisotropyAnisotropy directly with the directionally solidified microstructureMicrostructure, highlighting the critical need for process controlProcess control to produce reliable, load-bearing components with this emerging desktop technology.