sentences:  In the first three decades of the 20th century the Lighthouse Board and the new Lighthouse Service continued to build new lights on the Great Lakes.For 1925, the Board had under its auspices around the Great Lakes 433 major lights, ten lightships, 129 fog signals and about 1,000 buoys.Of these 1,771 navigational aids, 160 stations had resident keepers, as most navigational aids were automated.