The area was settled by the ninth century, when a small area in the middle of the Realtine Islands either side of the Rio Businiacus was known as the Rivoaltus. Soon, the Businiacus became known as the Grand Canal, and the district became the Rialto, referring to only the area on the left bank.
The Rialto became an important district in 1097, when Venice's market moved there, and in the following century a boat bridge was set up across the Grand Canal providing access to it. This was soon replaced by the Rialto Bridge.
The market grew, both as a retail and as a wholesale market and warehouses were built. Meanwhile, shops selling luxury goods, banks and insurance agencies appeared and the city's tax offices were located in the area. The city's abattoir was also in the Rialto.
Most of the buildings in the Rialto were destroyed in a fire in 1514, the sole survivor being the Church of San Giacomo di Rialto, while the rest of the area was gradually rebuilt. The Fabriche Vecchie dates from this period, while the Fabbriche Nuove is only slightly more recent, dating from 1553.
Early residents of Rialto prided themselves for the cultivation of muscat grapes and thus became an important contribution to the economy.
The prominent Rialto Trapp family bought the first school house in 1921, remodeled the building, and members of the family resided in it until it was destroyed by fire.
On September 13 2005 the Rialto city council voted to dissolve the Rialto Police Department and replace it with a contract with the San Bernardino County sheriff's department.