Insulating 120 Year Old House

[Halle Hughes]

I currently owner occupy a 120 year old duplex in Minneapolis, MN that I purchased in August of 2020. Now that winter is here, I've had the unfortunate realization that the original windows are extremely drafty and let in all the cold Minnesota air. Most of the windows are large, double hung windows, and the issue is that the sliding portion of the windows don't shut all the way/leaves a gap.The frame around the windows are in pretty good shape. Does anyone have recomendations to remedy this? Any good window/door companies or insulation companies that can service this issue in the Minneapolis area? Are there options for repair/restoration or do I need to bite the bullet and install brand new windows?

Thank you! 

Halle