Align edges of ggplot choropleth (legend title varies)

Question

I am attempting to align the left and right edges of 4 ggplot choropleth maps using this method. I am unable to do this though.

Original plot:

Answer 1

Using cowplot package:

library(cowplot)
plot_grid(plot1, plot3, plot2, plot4, ncol = 2, align = "v")