Cape Verde will be the first country to complete successfully a loan from the Millennium Challenge Corp, a US government-backed initiative that lends money to democratic countries, a US official said.
It signed a $110m deal under the initiative in 2005 to boost its economy, including through infrastructure projects and investment in agriculture.
In a sign of its Western inclination, Cape Verde agreed to be the site in 2006 of Nato exercises.
Clinton earlier visited South Africa, Angola, the Democratic Republic of Congo, Nigeria and Liberia.
In all of these countries, Clinton has been pushing for better governance across Africa.
She returns on Friday to Washington, closing the longest trip she has had since taking office in January.