Place potatoes into a large pot and cover with water; add salt and bring to a boil. Reduce heat to medium-low and simmer until potatoes are tender when pierced with a fork, about 30 minutes. Drain and set aside until cool enough to touch, but still warm.

Peel potatoes and cut into chunks. Place in a bowl and add eggs and onion. Mix in mayonnaise, celery salt, and pepper until well combined. Refrigerate until flavors have melded, about 1 hour. Serve chilled.