The biggest solar power plant in the country will be built in West Sacramento, after a Spanish solar development company chose the city for its U.S. headquarters, the company confirmed Monday. West Sacramento and its port, where the plant will be located, beat Oakland to grab the new national headquarters of Otras Producciones de Energia Fotovoltaico. The company develops solar power plants and manufactures the tracking systems solar panels are mounted on. The company's subsidiary, OPDE U.S. Corp., officially began operating on March 1 in a roughly 70,000-square-foot building at 1430 Enterprise Blvd. in West Sacramento. But OPDE isn't coming here alone. It's bringing along two more subsi