I followed this [post][1], the first answer, to clip a USGS Quad in order to remove the borders so that I can tile them. Basically it utilized the lat/long at the corners in a .txt file to import a rectangle using "add delimited text layer". I then reproject the rectangle to match the CRS of the USGS quad. After I clip it I get black edges, see image. 

![black corners][2]

I offered the error as a comment in the aforementioned post and it was answered that its likely from re-projecting the rectangle and that I should use -dstalpha or -dstnodata to make it white. When I use those two options, I just get a colored rectangle. I actually want that area transparent for when I tile multiple USGS Quad maps. I even tried to re-project the quad map to the CRS of the rectangle.

Does anyone know how I can clip the USGS quad without having the black corners for tiling pruposes? FYI... I am using QGIS 2.2 on Windows 7.


**EDIT:**

The mask that I have compiled using the delimited text layer matches the area that I would like to clip perfectly. So I dont think that I have an error. I downloaded the [Newburgh][3] and  the [Cornwall on Hudson][4] Quads. Reading the corner coordinates I developed the following two .txt files:

Newburgh

> Nr;WKT
1;POLYGON((-74.00 41.5, -74.125 41.5, -74.125 41.625, -74.00 41.625, -74.00 41.5))

Cornwall on Hudson

> Nr;WKT
1;POLYGON((-74.00 41.375, -74.125 41.375, -74.125 41.5, -74.00 41.5, -74.00 41.375))

  [1]: https://gis.stackexchange.com/questions/74980/cropping-and-transforming-geopdf-with-gdalwarp
  [2]: https://i.sstatic.net/iVlfl.png
  [3]: http://gis.ny.gov/gisdata/quads/drg24/bb46.htm
  [4]: http://gis.ny.gov/gisdata/quads/drg24/cc46.htm