Hello Brad!

The most likely cause of the crack in your Crimson King maple tree is a frost crack. Frost cracks are generally not fatal but they can weaken a tree and allow decay organisms to enter the tree.

Maple trees have thin bark and this makes them more susceptible to frost cracks, especially on the south or southwest side of the tree. Frost cracks are vertical cracks in the trunks of trees that occur when there are rapid temperature fluctuations. On warm, sunny winter days, the bark will warm up causing the cells to expand in the bark and wood directly below the bark. If the temperatures drop very quickly, the bark cools and contracts. The wood under the bark does not cool as quickly, causing the bark to split. A similar situation can occur during hot summer months when temperatures drop quickly at sunset. Again, the damage shows up on the southwest or south side of the tree because that’s where the sun rays directly shine on the trees. Once cracks have occurred in the bark it is important to continue to monitor it. With time the tree may begin to heal the cracked area by developing a callous. In fact, appears that your tree has a callous just above the crack in the third picture.

Here are some other gardening practices that may help support the health of your tree:

Add 2-3 inches of mulch of the root area of the tree, keeping mulch 5-6” away from the trunk

Water the tree during long dry spells in the spring and summer.

Avoid fertilizing in the fall

Another strategy to prevent frost cracks/sunscald is to plant smaller plants to help shade the south side of your tree.

https://www.canr.msu.edu/news/frost_cracks_and_winter_damage_to_trees

https://www.canr.msu.edu/news/frost_cracks_in_trees

Wishing the very best for you and your tree.