Measurements of magnetic moment g-factors and a anomalies a=(g-2/2) of the electron and muon provide precision tests of the Standard Model and may reveal new physics. The lepton magnetic moment g-factor is larger than the Driac value g=2 due to interactions with the quantum vacuum. The largest contributions, a/2π~10-3 are from QED, and have been calculated to 10th order, while the strong and weak interactions contributions are ~10-7 and ~10-9, respectively. Beyond-Standard Model Physics contributions mediated by heavy particles of mass scale mX are proportional to (ml/mx)2, which motivates study of g-2 for the muon. Over recent decades, aµ has been measured with increasing precision and theory has correspondingly improved, in particular in addressing hadronic contributions. Measurements at Brookhaven National Lab (BNL) for both positive and negative muons have precision 0.54 ppm, and the most recent theory compilation has precision 0.37 ppm. Tension of ~2.4 ppm or ~3.7 standard deviations motivated renewed experimental effort to move the magnet from BNL to Fermilab, develop an intense µ+ beam and the Fermilab Muon Campus, rebuild the experiment with state-of the art instrumentation, and support the analysis with simulations and a suite of new systematics studies. Analysis of the first year of data (Run 1) with statistics limited precision 0.46 ppm has recently been completed and is consistent with the previous result, increasing the tension to 4.2 standard deviations. In this talk I will describe the experiment and analysis in detail, present the result of Run 1, and discuss expectations for further measurements.
