There was a six-year gap, between 1975 (Apollo-Soyuz Test Project) and 1981 (first flight of the Space Shuttle), in which the United States did not have human space launch capability.
There is a six-year gap, between 2011 (last flight of the Space Shuttle) and 2017 (when the crewed Dragon and CST-100 are expected to launch).
There is a six-year gap, between 2011 (last flight of the Space Shuttle) and 2017 (when the crewed Dragon and CST-100 are expected to launch).