The objective of this phase II/III randomized clinical trial is to evaluate the efficacy of vitamin D therapy versus placebo in vitamin D-deficient African-Americans with hypertension, including investigating the relationship between vitamin D and cardiac damage (as identified on cardiac magnetic resonance imaging) in a vitamin D-deficient hypertensive patients without prior history of heart disease. Data include cardiac MRI and echocardiography data, lab results (e.g., vitamin D, CBC), and patient characteristics (e.g., vital signs, demographics, health insurance, education level, household income, hypertension drug and vitamin D treatment adherence, dietary intake, sun exposure).