[en] We report the first measurement using a solid polarized target of the neutron electric form factor Gⁿ_E via d-vector(e-vector, e'n)p. Gⁿ_E was determined from the beam-target asymmetry in the scattering of longitudinally polarized electrons from polarized deuterated ammonia (¹⁵ND₃). The measurement was performed in Hall C at Thomas Jefferson National Accelerator Facility in quasifree kinematics with the target polarization perpendicular to the momentum transfer. The electrons were detected in a magnetic spectrometer in coincidence with neutrons in a large solid angle segmented detector. We find Gⁿ_E = 0.04632±0.00616(stat)±0.00341(syst) at Q² = 0.495 (GeV/c)²