The STL has hash_map, but the C++ Standard Library does not.
Due to a common misconception, you may think of the C++ Standard Library as “the STL”, or of parts of your toolchain’s implementation of the C++ Standard Library as “an STL implementation”.
It is not.
It is also a great shame that both MSVC++ and GCC (which implement hash_map as a compiler-specific extension), place it in the std namespace, which is not only highly misleading, but also illegal per the standard. *sigh*
C++11 has introduced std::unordered_map, which is not dissimilar.