Final answer:
The last Marian apparition to Bernadette Soubirous occurred on July 16, 1858, and was the final one of 18 that began in February that year.
Step-by-step explanation:
The last Marian apparition that appeared to Bernadette Soubirous took place on July 16, 1858.
This event is part of a series of 18 Marian apparitions that occurred in Lourdes, France, which began on February 11, 1858.
During the final apparition, Bernadette felt called to the Grotto of Massabielle but found the grotto barricaded and guarded.
She witnessed the apparition from across the River Gave and described it as being as beautiful as before, lasting for a short time, and leaving her with a feeling of great peace.