string inLine = reader.ReadToEnd();
myList = inLine.Split(new string[] { "\r\n" }, StringSplitOptions.None).ToList();
This answer misses the original point, which was that they were getting an OutOfMemory error. If you proceed with the above version, you are sure to hit it if your system does not have the appropriate CONTIGUOUS available ram to load the file.
You simply must break it into parts, and either store as List or String[] either way.