From MINI USA PR:
MINI Brand Up 23 Percent Year-To-Date, Propelled by Best Retail Month
Demand for MINI brand automobiles was exceptionally strong as the division celebrated its third anniversary in the U.S. on March 22nd. March sales were the best ever recorded, for 4,127 cars versus 2,857 in March 2004, an increase of 44 percent. First quarter sales of MINI automobiles increased 23 percent with sales of 10,184 over the 8,271 sold in the first quarter of 2004.
As always, my complete list of MINI sales in USA has been updated.
In that data you can see that monthly MINI sales broke 4,000 only once before, achieving 4,005 sales in December 2003.
M&I / GBMINI 