In the book "A Stake in the Prairie" by the Mesquite Texas Historical Society it states:
Alanson Dowdy, born in Illinois, came to the colony as a single man but married before 1850. He claimed 640 acres, half of which he sold unlocated,a tract located the buyer, 5 1/2 miles south of the Beeman's tract, one corner reaching across the Trinity river. Years later a ferry was begun at this point and was called Dowdy Ferry, though we have no indication that Alanson Dowdy lived there. Later the crossing was bridged, and the road was called Dowdy Ferry Road. Dowdy located the tract which he kept in Robertson county , across the river.
This is now in Dallas County and south of the city of Dallas close to Interstate Hwy 45. I live close to the bridge and if I can be of any help please let me know.