The cross-correlation based HR-EBSD technique was used to derive stored geometrically necessary dislocation (GND) density in the OFHC copper samples deformed under uniaxial tension to true strain of 0%, 6%, 10%, 22.5% and 40%. Large maps (500μm x500μm with 0.5μm step size) with 1 million points and ∼1600 grains were acquired at each deformation level. Detailed studies on dislocation structure and evolution using the HR-EBSD were conducted. Distinct types of dislocation arrangements were revealed in grains with various orientations. For example, dislocation cells were formed in grains of <110> orientation and dislocation bands were generally found in grains of <111> and <001> orientations. The complicated dislocation networks provide vital evidence to understand the deformation mechanisms in polycrystals at mesoscale. Quantitative analyses were also carried out to study this GND density orientation dependence in which Taylor factor was used as an indicator to quantify the grain resistance to deformation. It was found that points with high GND content preferentially accumulated in grains with high Taylor factor (‘hard’ grains) in deformed samples. This relation becomes stronger with increasing deformation.