Line Under St Mary's Park in South Bronx, New York

My father, who lived in the south Bronx neighborhood of New York City from 1927 - 1953, and who worked for New York Central during the summers while in college and graduate school circa 1947-1952, reminded me that freight trains (either NYC or NH) ran thru a tunnel under St Mary's Park near his former home in the south Bronx.

I am told this line connected NYC Harlem Line in vicinity of (or just north of) Mott Haven Yard with NH line or New York Connecting RR in southeast Bronx, and was known as the Port Morris Branch.

Is that track still in service under CSX or possibly Metro North? If not, when was it abandoned?

The line you're talking about was the
Port Morris branch which branched off the Harlem line at the north end of Melrose station (162
St.) and went east.

It was abandoned about 10 (?) years ago when a new line was built along the extreme west shore of The Bronx (on pilings in the river, to be precise!) to access the freight yards in the Oak Point-Harlem River-Port Morris area. You can easily see this new line as you cross the Metro North lift bridge.

See also: http://nycshs.blogspot.com/2008/10/harlem-division.html