Eureka’s first street was surveyed down the gulch below the spring and named Main Street, with a broad avenue connecting it to Eureka Basin Spring. Because the street lay at a low elevation, water settled there, and heavy travel produced so much mud that it became known as “Mud” Street. Dozens of wooden buildings lined Main Street along a small creek that gathered runoff from the springs. Great fires in 1883 and 1888 destroyed most of the early buildings, after which owners quickly rebuilt stronger commercial blocks of limestone and brick at the same level along the creek and narrow street. In 1890, major street improvements added limestone walls that were filled and smoothed to create a wider surface for Main and Spring Streets, often raising the new roadways to the level of the second story in front of many business houses. As a result, a series of buildings along Main and the downhill side of Spring Street had their ground floors turned into basements, linked by narrow passageways that had once been storefronts, while most Main Street buildings also retained another basement level through which the little stream still runs.