diff --git a/configure.ac b/configure.ac
index f8114ff1..3740c298 100644
--- a/configure.ac
+++ b/configure.ac
@@ -5,6 +5,7 @@ AC_PREREQ([2.64])
 AC_INIT([IPhreeqc], [2.17.0], [charlton@usgs.gov])
 AC_CONFIG_AUX_DIR([config])
 AC_CONFIG_MACRO_DIR([m4])
+
 AM_INIT_AUTOMAKE([-Wall -Werror foreign subdir-objects])
 AC_CONFIG_SRCDIR([src/IPhreeqc.cpp])
 
@@ -14,6 +15,20 @@ AC_DEFINE(PHREEQC_CLASS)
 AC_DEFINE(USE_PHRQ_ALLOC)
 AC_DEFINE(NDEBUG)
 
+# libtool versioning
+# 1. Start with version information of ‘0:0:0’ for each libtool library. 
+# 2. Update the version information only immediately before a public release of your software. More frequent updates are unnecessary,
+#    and only guarantee that the current interface number gets larger faster. 
+# 3. If the library source code has changed at all since the last update, then increment revision (‘c:r:a’ becomes ‘c:r+1:a’). 
+# 4. If any interfaces have been added, removed, or changed since the last update, increment current, and set revision to 0. 
+# 5. If any interfaces have been added since the last public release, then increment age. 
+# 6. If any interfaces have been removed since the last public release, then set age to 0.
+IPQ_CURRENT=0
+IPQ_REVISION=0
+IPQ_AGE=0
+IPQ_VERSION=$IPQ_CURRENT:$IPQ_REVISION:$IPQ_AGE
+AC_SUBST(IPQ_VERSION)
+
 # Checks for programs.
 AC_PROG_CC
 AC_PROG_CXX
@@ -27,15 +42,15 @@ AC_ARG_ENABLE([fortran],
      [IPQ_FORTRAN=yes])
 
 if test "X$IPQ_FORTRAN" = "Xyes"; then
- AC_MSG_RESULT(yes)
- AC_PROG_FC
- AC_FC_LIBRARY_LDFLAGS
- AC_FC_WRAPPERS
- AC_FC_MAIN
- AC_SUBST(F77, $FC)
- AC_SUBST(FFLAGS, $FCFLAGS) 
+  AC_MSG_RESULT(yes)
+  AC_PROG_FC
+  AC_FC_LIBRARY_LDFLAGS
+  AC_FC_WRAPPERS 
+  AC_FC_MAIN
+  AC_SUBST(F77, $FC)
+  AC_SUBST(FFLAGS, $FCFLAGS) 
 else
- AC_MSG_RESULT(no)
+  AC_MSG_RESULT(no)
 fi
 AM_CONDITIONAL([BUILD_FORTRAN], [test "X$IPQ_FORTRAN" = "Xyes"])
 
@@ -49,6 +64,7 @@ AC_PROG_LIBTOOL
 
 # Checks for library functions.
 
+
 AC_CONFIG_FILES([
   Makefile
   src/Makefile
diff --git a/src/Makefile.am b/src/Makefile.am
index bb35e3d3..e8bc933f 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -1,9 +1,9 @@
 AM_CPPFLAGS=-I$(top_srcdir)/include -I$(top_srcdir)/src/phreeqcpp -I$(top_srcdir)/src/phreeqcpp/phreeqc
 
-
+# libtool libraries to build
 lib_LTLIBRARIES=libiphreeqc.la
 
-# library sources
+# library sources for libiphreeqc.la
 libiphreeqc_la_SOURCES=\
 	CVar.hxx\
 	Debug.h\
@@ -137,6 +137,10 @@ libiphreeqc_la_SOURCES=\
 	phreeqcpp/phreeqc/tidy.c\
 	phreeqcpp/phreeqc/transport.c\
 	phreeqcpp/phreeqc/utilities.c
+	
+# library sources for libiphreeqc.la
+libiphreeqc_la_LDFLAGS=-version-info $(IPQ_VERSION)
+	
 
 include_HEADERS=\
 	$(top_srcdir)/include/IPhreeqc.h\