Prohibition increased corruption in the United States during the early 1900's.
Prohibition was a period in which the sale and distribution of alcohol was illegal in the United States. This was done through a constitutional ban on production and sale of alcohol. It was outlawed but this did not prevent people from wanting to consume it. When there is demand for a good, even if it is outlawed, there will be supply.
People started to trade alcohol and since it was an illegal activity it gave big profits to those risking doing it and violence between trading groups started, just like with any other illegal activity. Gang groups started to compete for territory control over alcohol trading and this widespred in the country specially in big cities like Chicago with criminals such as Al Capone.
Corruption was a natural effect of this alcohol ban, since these criminal groups used bribes and corruption tactics to keep their illegal business running.