Simplify the following text for a Grade 9 native English-speaking person.
Original: Basseterre , estimated population 15,500 in 2000 , is the capital of the Federation of Saint Kitts and Nevis in the West Indies .
Simplified: Basseterre , had an estimated population of 15,500 in 2000 . It is the capital city of the Federation of Saint Christopher and Nevis , also called St Kitts and Nevis , in the West Indies .