Plot Question -- Attach Label / Legend to Series

[Jason Criss]

I plot multiple series on one plot by doing something like this:

plot(1:n,d2,1:n,d1);

I would like to label the data series d1 and d2 on the plot so that I can see which lines represent which series.  Anyone know how to do this?  I only see options to label x, y-axis and specific points on the plot.