Signilskär's location as Åland's second westernmost outpost towards Sweden, after Märket which lies directly on the border between Finland and Sweden, has played a major role during history.

At Signilskär there are today the ruins of a chapel which is believed to originate from the Middle Ages. In the ruins of the chapel, some silver coins we're found thats been dated from the 12th to the 13th century up to the 17th century. These coin is believed to have been used as sacrifical gifts. The chapel was restored in 1948.

Today, Signilskär is uninhabited. In addition to the chapel ruin, there are three buildings left, remains of an old windmill and a shallow harbor that was built in 1846. On the nearby island of Enskär there is a well-preserved pilot cabin from 1867 with a built-in, non-active lighthouse.

Signilskär, however, is best known for its bird life. Already in 1927 a station was established for studies of migratory birds on the island. The area around Signilskär is populated by many different kinds of sea birds that both nest and spends the winter on the island. Among the threatened species found in the area, sea eagles and herring gull can be mentioned.

A one way trip to Signilskär takes about 20 minutes with M/S Sefyr from Käringsund guest harbor.