From The Elevator Family Sets Sail:
Whitney held a small triangular flag that she had sewn. She attached the pennant it to a line and ran the flag up to the top of the tall mast in the center of the ship. On the flag was the Wilson’s logo. This way passing ships could tell who was on board the boat.
“The five stars are the Big W star formation found in the constellation Cassiopeia,” she explained.
“A constellation we’ve seen many times on our travels,” said Winslow. “Dad always says the Big W stands for Wilson.”
“And the Big W will again be guiding us during this voyage,” said Winona.
Captain Walter stood at the wheel. He wore his white captain’s hat. He leaned back to watch the Wilson pennant flap in the steady breeze. “Excellent, only the best. Yes, the Big W stands for our family"