The Marine Bank Company, which merged with the Bank One Corporation in the 1980s, was one of Milwaukee’s pioneer banks. Marine Plaza comprises a twenty-two-story rectangular block and a freestanding two-story lobby pavilion. It is Milwaukee’s best and first example of early curtain-wall construction, made possible by steel-frame construction. This isolated prismatic building breaks the city’s building line along the Milwaukee River, providing strolling areas and a pool for public meeting space. This resulted from a decision to fit the plans into the city’s redevelopment scheme for the Milwaukee River. An upturned slab on low piers, Marine Plaza hints at its internal structure with stainless steel mullions that trim green-tinted glass sheathing. The lobby pavilion is particularly impressive with delicate concrete piers supporting poured concrete vaults. Soaring glass windows usher in sunlight between the slender piers. A second-story banking hall has walls embellished by large mosaic murals, a rare example of an intact 1960s commercial interior. The sea-green glass exterior retains its original appearance, except for the new lobby entrance added to the N. Water Street elevation in 1994.