Sumter to Marlboro - ACL/SCL
The picture above (from the middle of the former ROW) shows the former ACL depot in Lamar, SC along the former Sumter - Darlinton segment of the line.  The depot has been well preserved by the business that occupies it now.  SAL also had a line into Lamar from Lydia, which continued on to Timmonsville.  The section from Timmonsville to Lamar provided the last rail service into Lamar until it was removed in the 1970s.  (Both pictures from December 2000)
This section of the Sumter - Darlington segment was abandoned in the mid 1950s.  It is located along US401 just north of the Lynches River (looking SW towards the river).  Some old rotting cross ties remain.
The line from Sumter to Darlington was built as part of the Charleston, Sumter & Northern in 1890.  It was hoped that the CS&N would become part of the SAL and its main line into Georgia and north Florida.  Read more about the history of the CS&N on the page about the North Western Railroad of SC.  The ACL bought the CS&N in 1895 through subsidiary Charleston & Northern and assigned this section to the Manchester & Augusta, which became the ACL after 1900.  This section was abandoned in the 1950s.  Sections of the ROW can still be made out in Sumter, along the Lynches River next to US401, and in Lamar.  The section from Darlington to Marlboro (south of Bennettsville) was also part of the old CS&N, and connected in Bennettsville with another ACL line from the A-line south of Fayetteville through Red Springs and Maxton, NC, through McColl, SC and into Bennettsville.  The section from McColl to Bennettsville to Marlboro remains in service as the Pee Dee RR.   A few pieces of the old ACL line from McColl to S of Fayetteville remain in service.  The old CS&N line from Bennettsville to Gibson, NC was shared with the Rockingham Railroad in the ACL era, but has now been abandoned N of Breeden near Bennettsville.  The section from Darlington to Marlboro was abandoned in pieces, with the last section being abandoned in the late 1970s by Seaboard Coast Line.  The ROW can still be made out in some places, particularly in Darlington.
A short distance N of the picture to the left, the old ROW can clearly be seen along Loring Place just E of Lafayette Drive.  This was the end of the portion that remained in service until the 1970s.  The old SAL wye was in the vicinity of the tree line at the end of the cleared ROW.  It is not known what this area looked like when both the SAL wye and the ACL line were in place (did the wye cross the ACL line?).
Along Grier Street just N of US 401 (Calhoun Street), you can still make out the ROW.  This portion of the former Sumter-Darlington line remained in place until the 1970s as it was used to access the former SAL Sumter-Bishopville line.  Before the ACL-SAL merger, it was used to exchange cars between ACL and SAL.
Winkles Road to the NE of the US 76/378 bypass, looking SW towards Sumter.  This is the former ROW of the Sumter-Darlington ACL line.  The ROW cannot be made out on either end of Winkles Road as it has either grown over or been built over with neighborhoods.  This segment runs from North Pike Road (the frontage road of the bypass) to Brewington Road.  (all three pictures from February 2001)
The Last Ride on the Sumter - Darlington Line!

Special thanks to Frank Bagnal of Sumter for this account.  See clarifications and follow-up to this story at the bottom:

Daddy and Joe were probably the last passengers on the Sumter -
Darlington ACL line.

One night, while the tracks were being taken up somewhere up the line
toward Darlington, a dinky engine, little more than a glorified tractor
with an engineers cab, was working the line hauling into Sumter the
rail, in gondolas, for spotting in the Sumter yards.

Daddy and Joe, having closed the store at 7 pm, nd gotten out around
7:30, came along Charlotte Ave to the ACL crossing, just in time to see
the little engine about to depart to head up the line for another load.
They asked, were told that the next gondola was "just up the line a
little piece" snd then asked could they ride.

Sure.

Not until they were on board and in motion, and well out of town, did
the two-man crew close the sliding windows against the breeze, and the
smell hit Daddy & Joe.  The crew was sauced.  Plastered.  Zonked.

When they weren't home by 10 pm -- no answer at the store -- somebody
had seen Daddy's car parked, lights off and locked, in the shadows
where they left it.

Mother -- and all of us -- were abot to have a stroke -- when in they
came.

The little engine, puttin' along at a crawl, just kept on, mile, after
mile -- wth the crew all jolly and having a good time, and Daddy and Joe
warily enjoying the last ride on the line, but it went on, and on, and
on.

Finally, Joe asked just how far was the gon.

I forget the answer --- but it might just as well had been in New York,
at the speed they were crawling.

It took allot of coaxing and $20 bucks - an "ouch" amount back then --
to get the inebriates to reverse direction and putt, putt back to town.

Follow-up from Frank Bagnal:

Joe can't remember for sure where they were headed but  it was not for another gondola ... they were finished for the night and going "home", probably to Hartsville.

Also, it was the groundman who was tipsy (not drunk) and who told Joe
they were going "just up the line for another load", but the engineer,
a younger man, was OK, and did not hear what the groundman told Joe.

They only got a little beyond Rocky Bluff Swamp before Joe asked the
engineer, and the problem was not ther hesitancy to return, but they
were low on fuel.  I forget to ask about the money given them.

Other Q/A I checked by phone:

was the engine / crew RR or contractor?
the latter.

what kind of engine?
gasoline powered, like Montague's once had.

when did you get home?
after 9:00pm

about how fast were you running?
twenty mph.

The real zinger was that, when they first got on board, Joe used an oil
drum for a seat, and quickly found out that the cover had a puddle of
oil on it, so Joe had oil-soaked pants for the trip.