The Via de la Plata was Rome's great north-south artery through western Iberia, and Salamanca sat squarely on its path. The exact date the bridge was built remains debated, with estimates ranging from the reign of Augustus in the late first century BCE to the early second century CE under Trajan and Hadrian. Some historians see structural similarities to the Aqueduct of Segovia; others rely on milestones along the road to date the construction. What is certain is that by the time Emperor Augustus launched his second military campaign in Hispania between 16 and 13 BCE, settlements were growing along these roads, driven by ore transport and the exploitation of gold mines at Las Cavenes. The bridge may originally have been a hybrid of stone and wood, only becoming the fully stone structure visible today through later rebuilding.

The Tormes was feared. In the early 16th century, it ranked alongside the Tagus as one of the most hazardous rivers on the Iberian Peninsula, prone to devastating floods. In 1498, the Avenida de Santa Barbara swamped the bridge. In 1626, the Flood of San Policarpo hit far harder, destroying two medieval arches and gradually bringing down others up to the bridge's central tower. Yet the Roman section survived undamaged, a testament to engineering that had already outlasted an empire. Repairs in 1627 replaced the fallen arches and removed the central tower and battlements. By 1767, another major restoration maintained the balance: eleven modern arches on one side, fifteen Roman originals on the other. In 1570, the artist Anton van den Wyngaerde painted the bridge and city from the suburbs, providing a visual record of what the structure looked like before the great floods reshaped it.

On 21 July 1812, the day before the Battle of Salamanca, the Duke of Wellington captured the Roman bridge along with nearby fords at Santa Marta and Aldea Luenga. From this position he directed British and Portuguese forces against the French troops of Napoleon's army in the hills of Arapil Chico and Arapil Grande, just south of the city. The battle proved a turning point in the Peninsular War. For the bridge, it was another chapter in a pattern stretching back to antiquity: whoever controlled this crossing controlled access to Salamanca. The bridge had served Roman legions, Visigoths, and medieval kings. Now it served a British duke fighting a French emperor on Spanish soil.

The bridge remained the main road into Salamanca until the early 20th century. Cars, carts, and livestock all crossed where Roman soldiers once marched. In 1973, with modern vehicular bridges built elsewhere in the city, the Roman bridge was closed to motor traffic and became a pedestrian crossing. Today it is a place for evening walks, where the golden stone of Salamanca's old town glows in the late light and the twin towers of the New Cathedral rise above the roofline. The bridge was designated a Bien de Interes Cultural in 1998. Artists have been drawn to it for centuries, from David Roberts in 1837 to Gustave Dore in 1862, and it serves as the setting for Miguel de Unamuno's 1914 novel Niebla. But no painting or novel quite captures the simple fact of the thing: a functional bridge, still in daily use, built before the Roman Empire reached its peak.