Shares of D.R. Horton were up slightly on the news at around $34.62 before noon on Tuesday.
Under the deal, Westport will operate as a separate division within D.R. Horton, which has operations in 81 markets in 27 U.S. states and owns several brands.
The company said that the buy of Westport -- which operates largely in Indianapolis and Ohio -- would expand D.R. Horton by thousands of lots and hundreds of homes.
"Their well-established building operations make Westport a great fit for D.R. Horton as we expand our footprint in the Midwest," said Donald R. Horton, D.R. Horton's chairman, in a press statement.
By the 12 months ended Oct. 31, Westport had closed 886 homes with average sale prices of $264,000, and closed the period with $234 million in revenue.