> What is the history of bacon, was it always cured with sugar?

One method of curing meat (bacon, jerky, salmon, corned beef, etc.)
requires that you soak the meat in a brine solution.  For things
like smoked salmon or bacon, you soak in the brine prior to smoking
or before drying (for jerky).  Salt and sugar are both included in
most brine solutions for their antibacterial properties.  Most
microorganisms cannot tolerate much of either because it affects the
osmotic pressure of the cell wall.  Salt and sugar will help retard
mold during the rest of the curing process and after.

Smoking your own bacon and using it up or freezing it right away
would allow you to bypass the brine stage.