The issue is occuring before the data is loaded into tableau so changing the format type within tableau wont help as the data has been dropped during import.
The reason for this is that data from sources such as excel and csv files are initially processed using the microsoft jet engine and this can result in the miss-classification of columns as it doesnt review every row. This can result for example in a column being defined as numeric, then when text is encountered the row is dropped from import.
You can get around this by creating a schema.ini file that will instruct the system how to handle the columns. This article should help;
Thanks, Andy!! That article was exactly what I needed. I actually took one of the simpler solutions it offered and moved one of my rows with the text value in the Year field to be the first row of the data. Refreshed my extract and it all works exactly as I need it to!