The old name Samignana first appeared in the 12th century and was maintained until the 18th century. The estate was under the rule of a Sannazzaro family line, but the Reyna family of Spanish origin from Pavia was partly enfeoffed with it in 1470. The Sannazzaro and the Reyna families were still sharing the estate in 1707. That year, Semiana, with the rest of the Lomellina, passed under the dominion of the House of Savoy (formally in 1713). It was annexed to the province of Pavia in 1859 and, in the early 19th century, the old community of Ferretto – hardly inhabited in the earlier century, today no more than a farmhouse – was attached to Semiana.