The main agricultural products are tomatoes, cotton, wheat, almonds, peanuts and pistachio nuts.

During the Middle Ages, sources refer to "two Halmyroi" (δύο Άλμυροι): one of these was at the same site as ancient Halos, 6 km southeast of the present-day town of Almyros, while the other was an associated port on the Pagasitic Gulf.

[3]: 171 Medieval Halmyros owed a lot of its prosperity to the presence of Italian merchant groups who settled here (originally from places like Venice, Pisa, and Genoa).

In 1198, the "two Halmyroi" were mentioned for the first time, in a document under Alexios III Angelos granting special privileges to the Venetians.

In the 1204 Partitio terrarum imperii Romaniae after the sack of Constantinople, the "duo Almiri" are mentioned among the Thessalian possessions of Alexios's wife, Euphrosyne Doukaina Kamatera.

Halmyros was then assigned by Boniface of Montferrat as the place where the former Alexios III would reside as a private citizen.

Later, Halmyros became a property of William of Larissa and later still was assigned to Margaret of Hungary, Boniface of Montferrat's widow.

Halmyros was sacked in 1307, and in 1310 it was captured by the Catalan Company along with several other towns in southern Thessaly (namely Domokos, Gardikia, and Pharsalos).