The US Centennial coins will be available for purchase on January 17th, 2018. The .900 fine silver dollars are priced at $48.95 (uncirculated) or $53.95 (proof). These prices will rise by $5.00 after February 17th. A portion of the purchase price goes to help fund the National WW1 Memorial at Pershing Park in DC.
For more details go to this website.
These coins must be purchased directly from the US Mint . They are not available from KansasWW1.org.