Work began on the Olmos Dam and bypass channel in 1926; however, the San Antonio Conservation Society successfully protested the paved sewer option. No major plans came into play until 1929, when San Antonio native and architect Robert Hugman submitted his plans for what would become the River Walk. Although many have been involved in development of the site, the leadership of former mayor Jack White was instrumental in passage of a bond issue that raised funds to empower the 1938 "San Antonio River Beautification Project", which began the evolution of the site into the present 2.5-mile-long (4 km) River Walk.

What is the length of the riverwalk in san antonio? OK. Let's think. My stream of consciousness:
To answer the question, consider the following: Although many have been involved in development of the site, the leadership of former mayor Jack White was instrumental in passage of a bond issue that raised funds to empower the 1938 "San Antonio River Beautification Project", which began the evolution of the site into the present 2.5-mile-long (4 km) River Walk. The answer is 2.5 - mile - long ( 4 km ).