This is the closeout report for the grant for experimental research at the energy frontier in high energy physics. The report describes the precise measurement of the W boson mass at the CDF experiment at Fermilab, with an uncertainty of ≈ 12 MeV, using the full dataset of ≈ 9 fb-1 collected by the experiment up to the shutdown of the Tevatron in 2011. In this analysis, the statistical and most of the experimental systematic uncertainties have been reduced by a factor of two compared to the previous measurement with 2.2 fb-1 of CDF data. This research has been the culmination of the PI's track record of producing world-leading measurements of the W boson mass from the Tevatron. The PI performed the first and only measurement to date of the W boson mass using high-rapidity leptons using the D0 endcap calorimeters in Run 1. He has led this measurement in Run 2 at CDF, publishing two world-leading measurements in 2007 and 2012 with total uncertainties of 48 MeV and 19 MeV respectively. The analysis of the final dataset is currently under internal review in CDF. Upon approval of the internal review, the result will be available for public release.