Combine raisins and rum in bowl. Let sit 2-24 hours (the longer the stronger).
In a large bowl, whisk together the flour, cinnamon, baking soda and salt; set aside.
In the bowl of a stand mixer fitted with the paddle attachment or in a large mixing bowl using an electric mixer, cream the butter, brown sugar and granulated sugar together for 1-2 minutes until well-combined. Add in the egg and vanilla extract, and mix until fully combined.
Slowly mix the flour mixture and continue mixing until just combined. Add the oats and raisins, and mix until fully combined, making sure to scrape down the sides of the bowl as needed.
Cover the cookie dough tightly with plastic wrap and refrigerate for 30 minutes.
Meanwhile, preheat the oven to 350°F. Line two large baking sheets with parchment paper or silicone baking mats and set aside.
Once the dough is chilled, remove it from the refrigerator and scoop out 2 tablespoon-sized balls of cookie dough onto the prepared baking sheets. Make sure to leave a little room between each ball of cookie dough as they will spread a little while they bake.
Bake in separate batches for 10-12 minutes or until the edges of the cookies are lightly golden brown and the tops are set. Remove from the oven and cool on the baking sheet for 5 minutes, then transfer the cookies to a wire rack to finish cooling.