in the 1830s, at the peak of the canal-building era, hydropower was used to transport barge traffic up and down steep hills using inclined plane railroads. for direct mechanical power transmission industries that used hydropower had to be near the waterfall. for example, during the last half of the 19th century, many grist mills were built at saint anthony falls, to use the 50 foot (15 metre) drop in the mississippi river. the mills were important for the growth of minneapolis. today the largest use of hydropower is for electric power generation. that allows low cost energy to be used at long distances from the watercourse.