Field monitoring is the only effective approach to grasp the stress and deformation of large caissons during the sinking process. Taking the north anchorage caisson of a Yangtze River Bridge—the world’s largest onshore caisson—as the research object, the geometric posture, earth pressures, stresses of the steel shell and steel bars, and settlements of the surrounding environment of this caisson during its sinking process were introduced and analyzed in detail. The results show that the sinking rate of a large caisson is closely related to the construction process. When a caisson enters a stable sinking state, better soil properties correspond to a slower sinking rate. Auxiliary sinking measures (e.g., air curtains) would be required in the final stage to sink a large caisson to the design elevation. Postsinking construction activities (e.g., bottom sealing, filling, and the construction of the top cover and upper anchorage) induce additional settlement and tilting of a caisson. The bottom earth pressure first increases and then decreases as the sidewall frictional resistance develops. When the sinking depth exceeds the critical depth, the distribution of sidewall earth pressure evolves from a linear increase to a convex pattern (larger in the middle and smaller at both ends) along the caisson depth. For a large caisson, concrete typically develops cracks during the sinking and service process. However, the protective effect exerted by the caisson’s steel shell and internal steel bars effectively mitigates the adverse impacts of these cracks, which could ensure that the overall structural safety and load-bearing capacity of the caisson are not compromised. The settlement of the surrounding environment correlates with the distance from the caisson—the farther the distance, the smaller the settlement. For a large caisson, the influence range of sinking may exceed three times the sinking depth.