So, I've read around quite a bit and have come across the ActiveWorksheet.UsedRange function, as well as clearing all contents and deleting rows.
My worksheet has two sections to it; A1:AJ2900 and AL1:BX2900 - The second section is used to paste raw data, and the first section uses formulas to cross-reference the raw data across multiple sheets.
When I hit CTRL + End, I am taken to BX1048576.
I have tried the following:
Select rows 2902 - 1048576 > Clear All
Select Rows 2902 - 1048576 > Right Click row header > Delete -- When I do this, the formats of A1:AJ1 are copied and pasted to A2902:AJ1048576, when they were previously clear of formats.
ActiveSheet.UsedRange
Edit: Per this: https://support.microsoft.com/en-us/kb/244435, I have added the Excess Format Cleaner add-in.
After each of these, I saved the document and re-opened. No change.
I want to say that this happened before and there was a setting in Excel Options that did something? I might be thinking back to OpenOffice though, when I still used that.