Due to its location alongside a maritime trade route, it was important to seafaring nations that Vilsandi have some shelter for shipwreck survivors.

Over time, as the letter “ä” was not familiar to the various non-Estonian seamen in the area, some family members changed Mänder to Mender because it was easier to spell.

In 1931 a seabird museum was built on Vilsandi and before World War II (1939–1945) there were about 200 permanent residents on the island and about 3,000 – 5,000 tourists that would visit during the summer months.

[2] During World War I, in October 1917, Germany launched Operation Albion, a massive fleet of over 300 ships and 25,000 soldiers, to occupy Saaremaa and other Baltic islands to try to force Russia, who governed Estonia at the time, to surrender.

[3][4] In 1941, Toom was arrested by the Russians, accused of undertaking counterrevolutionary activities and spying for capitalist countries, and was sent to a Stalinist work camp where he perished in 1942.

Vilsandi has produced 16 ship captains or Master Mariners, some of whom were related to Peeter All (1829–1898), a noted resident of the nearby island of Loonalaid.

Kalmar, Mender and Roos worked in the Russian Far East and China prior to World War II and in 1930 co-founded the Estonian shipping firm Merilaid & Co.[5][6] On 19 September 1944 about 40 of Vilsandi's 155 inhabitants escaped by boat to Sweden, evading a blockade by the Kriegsmarine.

In 1945, after World War II had ended, the Soviet Union designated all of the islands around Vilsandi a restricted area closed to the public for national security reasons.