The Event Horizon Telescope (EHT) Collaboration presented the first resolved linear and circular polarimetric images of Sagittarius A* (Sgr A*), the supermassive black hole at the Galactic center. These images, derived from 2017 EHT observations at 230 GHz, reveal a bright, thick ring with a diameter of 51.8 ± 2.3 μas and a highly polarized structure. The linear polarization shows a prominent spiral pattern with a peak fractional polarization of ~40% in the western portion of the ring. Circular polarization features a dipole structure with negative polarization in the west and positive in the east, though the results are less consistent than for linear polarization. The data were analyzed using multiple imaging and modeling methods, validated with synthetic data sets. Despite intrinsic variability, the polarization structure is robust to methodological choices. The results provide stringent constraints on the black hole and its magnetic fields. The study also addresses challenges such as interstellar scattering, time variability, and Faraday rotation, which were mitigated through calibration and data processing techniques. The polarization measurements support models of a low accretion rate and provide insights into the accretion physics and spacetime near the black hole. The findings are discussed in an accompanying paper, highlighting the importance of polarization in understanding the environment around supermassive black holes.The Event Horizon Telescope (EHT) Collaboration presented the first resolved linear and circular polarimetric images of Sagittarius A* (Sgr A*), the supermassive black hole at the Galactic center. These images, derived from 2017 EHT observations at 230 GHz, reveal a bright, thick ring with a diameter of 51.8 ± 2.3 μas and a highly polarized structure. The linear polarization shows a prominent spiral pattern with a peak fractional polarization of ~40% in the western portion of the ring. Circular polarization features a dipole structure with negative polarization in the west and positive in the east, though the results are less consistent than for linear polarization. The data were analyzed using multiple imaging and modeling methods, validated with synthetic data sets. Despite intrinsic variability, the polarization structure is robust to methodological choices. The results provide stringent constraints on the black hole and its magnetic fields. The study also addresses challenges such as interstellar scattering, time variability, and Faraday rotation, which were mitigated through calibration and data processing techniques. The polarization measurements support models of a low accretion rate and provide insights into the accretion physics and spacetime near the black hole. The findings are discussed in an accompanying paper, highlighting the importance of polarization in understanding the environment around supermassive black holes.