 As a result, many 17th century maps showed a rather strangely shaped Sakhalin, which included only the northern half of the island (with Cape Patience), while Cape Aniva, discovered by de Vries, and the "Black Cape" (Cape Crillon) were thought to be part of the mainland.It was not until the 1787 expedition of Jean-François de La Pérouse that the island began to resemble something of its true shape on European maps.Though unable to pass through its northern "bottleneck" due to contrary winds, La Perouse charted most of the Strait of Tartary, and islanders he encountered near today's Strait of Nevelskoy told him that the island was called "Tchoka" (or at least that is how he recorded the name in French), and it was used on some maps thereafter.