Costa Valle Imagna (Còsta in dialect bergamasco) seems to have been inhabited throughout the year only from 1300 onwards. Previously it was probably only a mountain pasture for cattle occupied during the summer months. In fact the winter climate of Costa is rigid saw that the country is oriented toward the northeast side of the valley, so much so that coast is said the nevera of the Imagna Valley. For reasons of communication The country has long been more linked with the San Martino Valley, Almenno San Salvatore and the plain that with the rest of the Imagna Valley.
With the annexation in 1428 in the province of Bergamo to the Republic of Venice, the country came to be on the border between the Serenissima and the Duchy of Milan. As evidence of this the stranger is said in the dialect of Costa bir (henchman), with probable reference to the customs officials sent from Venice to patrol the border. At the time of the Counter-Reformation is found an episcopal ratio, which regretted the bad state it was the parish church because of the poverty of the village. Coast was also hit by the plague of Manzoni's memory of 1630, as proved by the discovery of a common burial. Until 1864 the municipality retained the name of Costa and after that date it took the name of Costa Valle Imagna.
Since the beginning of the twentieth century Costa Valle Imagna is also known as a holiday resort. The village is situated on the top right side of the Imagna Valley, Da Costa is therefore possible to enjoy a wide view, in particular, turning our gaze to the north the eye falls on the impressive Mount Resegone. Reaching the fraction of the fork and the pitch of the Pertüs (m 1186) our gaze extends over the whole Brianza and in favorable days, up to Milan. There is still in fact anyone who recalls that during the II world war, from Pertüs were visible, at night, fires caused by Allied bombing raids on the Lombard capital.