This web page lists some important American think tanks.
"The RAND Corporation is a nonprofit institution that helps improve policy and decision making through research and analysis."
The American Enterprise Institute (AEI) seeks to "defend the principles and improve the institutions of American freedom and democratic capitalism” through limited government, private enterprise, individual liberty and responsibility, vigilant and effective defense and foreign policies, political accountability, and open debate.
Brookings Institution: "Brookings Institution is a nonprofit public policy organization based in Washington, DC. Its mission is to conduct in-depth research that leads to new ideas for solving problems facing society at the local, national and global level."
Center for Strategic and International Studies
One of the most respected think tanks in Washington. Since 1962, CSIS has maintained its stated mission of “finding ways to sustain American prominence and prosperity as a force for good in the world” by providing non-partisan policy analyses on issues such as international relations, trade, technology, finance, energy, and geo-strategy.