Joe Biden is using the first visit to Angola by a U.S. president to promote Washington’s hefty modern investments in the sub-Saharan Africa nation and to see a slavery museum where he’ll acknowledge how the trafficking of human beings once linked the nations’ economies. A centerpiece of his trip is the U.S. having committed $3 billion to the Lobito Corridor, a railway redevelopment linking Zambia, Congo and Angola and meant to make it easier to move raw materials around the continent, and for export. Biden will tout that project. He'll also visit the National Slavery Museum and plans to acknowledge the history of slavery that has connected the U.S. and Angola.