Lines to Polygon to Raster in R & QGIS

I want to provide details the process of converting a line shapefile to a polygon using both R and QGIS.  I found a line shapefile of the everglades, and wanted to eventually have a raster where all cells within the national park (raster) are given a value of 1 like this:

 The line shapefile in QGIS

The line shapefile in QGIS

 The raster with all cells in the park set to 1

The raster with all cells in the park set to 1

 Not quite...

Not quite...

First, I imported to the line shapefile of ENP into QGIS and converted it to a polygon using VECTOR >> GEOMETRY TOOLS >> LINES TO POLYGON. The resulting polygon was a bit messy. Certain portions of the park were inverted. To the rescue--the node editing tool (picture below).  I selected problematic nodes that caused the automated process to invert certain regions.  I dragged and added nodes where necessary until the final shapefile looked exactly like the originaly imported line shapefile.

 The final polygon for Everglades National Park

The final polygon for Everglades National Park

 
 
 The node tool to the rescue!

The node tool to the rescue!

library(rgdal)
library(raster)

## Import the new shapefile
everglades_boundary <- readOGR(dsn = ".", layer = "everglades_newest")

## Create a raster that has the extent of the shapefile, and also set desired resolution/projection.
everglades_boundary_raster <- raster(ext = extent(everglades_boundary), crs = projection(suitability_map_as_raster_20_sec), res = 0.005555556)

## Set all values of the raster to 1
values(everglades_boundary_raster) <- 1

## If you plot the raster it will look like a sqaure (that's fine for now!)
plot(everglades_boundary_raster)

## Here, use the very helpful mask() function to retain only raster cells within the park boundaries.
everglades_boundary_outline <- raster::mask(everglades_boundary_raster, everglades_boundary)
plot(everglades_boundary_outline)