books.google.com - In Colonial times, as the Chesapeake Bay and larger rivers became vital shipping channels, the need arose to mark Maryland's dangerous shoals and waterways. Lighthouses sprang up throughout the 1800s and early 1900s, including wood-framed cottages placed upon screw pile foundations that stood offshore...http://books.google.com/books/about/Maryland_s_Lighthouses.html?id=m_LuqoTfCbEC&utm_source=gb-gplus-shareMaryland's Lighthouses
