La Unión is situated in the Region of Murcia in the southeast of Spain. It has an area of 24.6 km². It has a population of 16,180. It has the elevation of 86 m. Its average annual temperature is 17 °C. It has balmy winters. The sun shines 320 days per year. La Unión is situated in one of the sunniest areas in Europe; this kind climate makes possible the many leisure activities, popular fiestas, sports, and cultural activities that are held in the town. The town is linked by regular train to Cartagena which allows views of the past industrial heritage of the area (lead, alum and silver mining) and the more modern occupations of agriculture and tourism.