According to Official Guinness Records,
The longest chain of marker pens consists of 7,210 pens and was achieved by Carine Primary School (Australia) at their campus in Carine, Western Australia, Australia on 30 October 2014. The marker pens were connected vertically and the length of the line was 77.29 m (253.58 ft)
For a complete list of 2014 records, please visit 2014 Guinness Records in Australia.