I would call it a traditional spiritual song. Ry Cooder has several good versions on youtube
Wash Hobson Sr. from Rockford IL.
It indicates that it is a spur off of the mainline highway (Interstate 76). In this case it does not reconnect to the mainline but to a different mainline (Interstate 95).
It means the death of Jesus.
The term "mainline merchandising" is a reference to the product flow. Usually the main line begins with the production of the product and ends with the distribution of the product.
I guess it's about Jesus
Though Neutral Milk Hotel does have a song about Jesus Christ, they are not Christian. On a live version of the song, Jeff Mangum states before he plays "Here's a song about Jesus. I mean, I'm just as confused as everybody else... but it's always nice to sing a song about Jesus."
It's about loving Jesus so much you don't care if people call you a freak. If you love Jesus and give your life to him you become a Jesus Freak.
Mainline Steam was created in 1988.
Mainline Airways ended in 2003.
Midland Mainline ended in 2007.
Midland Mainline was created in 1997.